You send the same brief to two agencies. One quotes £8,000 / $10,000. The other quotes £45,000 / $60,000. The natural assumption is that somebody’s wrong, that one is ripping you off or the other is cutting corners. Usually, neither is. They’ve read the same document, made different assumptions about what it requires, and priced those assumptions honestly.
The gap between the two numbers isn’t a mystery. It’s a disagreement about scope, risk, method, and margin that neither quote makes visible.
This piece pulls apart the places where those disagreements hide.
They read your brief differently
Same brief, different interpretations. A document that says ‘we need an ecommerce site with around 200 products’ is a Shopify template job to one agency and a custom WooCommerce build with ERP integration to another. Both readings are legitimate. The first agency assumed a catalogue with standard checkout. The second noticed you’re a B2B wholesaler with tiered pricing and assumed you’d need that reflected in the build.
Vague briefs produce wider gaps, because each agency fills the ambiguity with its own experience
A brief that specifies ‘200 SKUs, trade and retail pricing tiers, integration with Sage 200, delivery calculated by weight and postcode’ compresses the range. It eliminates the biggest interpretation gaps before anyone starts estimating.
We’ve seen briefs where one agency priced 15 pages and another priced 45 for the same project. The brief listed ‘key services’ without a number. One agency took that literally. The other ran a content audit and realised the client had 30 services across four divisions. Both were trying to do the right thing. The brief let them reach completely different conclusions.
How much pre-build work is priced in?
This is the single largest variable we see between quotes, and the one buyers most often overlook.
One agency includes a £2,000 / $3,000 discovery line item: a half-day workshop, a sitemap, a wireframe set, and a documented scope before design starts. Another includes £8,000 / $10,000 of discovery covering user research, analytics audit, content strategy, information architecture, and stakeholder interviews across two departments. A third includes no discovery at all and starts designing in week one.
All three will write ‘discovery’ or ‘scoping’ on the proposal. The word is identical. The work behind it varies by a factor of four. We’ve written separately about what a discovery phase actually involves and when it’s worth paying for, but the point here is simpler: if you’re comparing two quotes and one is £15,000 / $20,000 higher, check how many hours of thinking happen before anyone opens a code editor. That’s often where most of the gap lives.
Who carries the risk when scope shifts?
Fixed-price quotes transfer risk to the agency. The agency estimates the work, adds a buffer for the things that will go wrong, and absorbs the overrun if the buffer isn’t enough. That buffer is real money. On a £30,000 / $40,000 fixed-price project, the contingency baked into the quote might sit between £4,000 and £6,000 ($5,000 and $8,000), depending on how well the agency knows the platform and how clear the brief is.
Time-and-materials quotes transfer risk to the buyer. The agency charges for the hours it works, and if the scope grows, the invoice grows with it. The headline number looks lower because there’s no contingency padding. But the final cost depends entirely on decisions the buyer hasn’t made yet.
Neither model is dishonest. They’re pricing risk differently. A fixed-price quote of £35,000 / $45,000 and a T&M estimate of £25,000 / $33,000 might produce the same final cost if the project runs as expected. The fixed-price agency has priced in the chance that it won’t. The T&M agency has left that chance with you.
When you’re comparing a fixed-price quote against a T&M estimate, you aren’t comparing value. You’re comparing different financial instruments.
What does the team actually look like?
A two-person studio where the founder designs and a senior developer builds will quote differently to a 15-person agency that assigns a project manager, a UX designer, a UI designer, two developers, and a QA tester.
The larger team isn’t padding the invoice. Each role exists because the agency has decided that role reduces risk or improves the output at that scale of project. But the cost of six people working across eight weeks is structurally different to the cost of two people working across six weeks. The output might be comparable. The process and the communication overhead are not.
Seniority matters too. An agency that puts a developer with 12 years of WooCommerce experience on your project will charge more per hour than one staffing a mid-level developer who’s competent but slower. The senior developer might finish in 60 hours what takes the mid-level developer 100. The total cost could end up similar, but the per-hour rate on the quote looks completely different, and the per-hour rate is usually what buyers fixate on.
Ask who will actually work on the project. Names, roles, rough seniority. If the quote doesn’t tell you, the agency is pricing a resource allocation model, not a team.
Are they pricing what you asked for, or what you need?
Some agencies quote the brief as written. If you ask for a five-page website, they’ll build a five-page website. If that turns out to be the wrong solution for your problem, you’ll discover that after launch.
Other agencies interrogate the brief before quoting. They’ll come back with questions, sometimes recommending a different platform, a different structure, or a phased approach that delivers a smaller site first and expands later. This takes time. That time is reflected in the quote, either as a separate scoping fee or as a higher project price that accounts for the strategic thinking.
The second approach costs more upfront but tends to cost less over three years. We’ve seen organisations pay £8,000 for a site they outgrew within 14 months, then spend £22,000 rebuilding on a platform that should have been the choice from the start. The agency that would have quoted £18,000 initially, with the right platform and a content migration plan, looked expensive at proposal stage. It was the cheaper option by year two.
The line items you’ll never see on the invoice
Agency overheads vary enormously, and they land directly on your quote. A creative agency in central London, Bristol, or Manchester with 10+ staff, an office lease, employer’s NICs, pension contributions, professional indemnity insurance, and a project management layer has a cost base roughly 2 to 3 times its direct billable salary cost through client fees once overhead, non-billable time, and profit are included.
Neither setup is better in the abstract. The larger agency’s overheads fund the infrastructure that handles complex projects: the PM who chases your content deadlines, the QA process that catches the broken form on mobile before your customers do. Whether you need those things depends on the project. They’re in the quote whether they’re visible or not.
Profit margin is the other invisible line. Industry benchmarks for UK digital agencies put net margins around 10% to 20%, with well-run agencies targeting the higher end. A £30,000 quote from an agency running at 15% margin has £4,500 of profit built in. That is the agency’s reason for existing. Asking agencies to compete on margin is a race that ends with corners cut on your project, or with the agency going under mid-build. Both outcomes are worse than the original quote.
How to actually compare quotes that are £30,000 apart
Stop comparing the total. Start comparing the assumptions.
Ask each agency to break the quote into phases: discovery, design, build, content, testing, launch, post-launch support. If one agency’s build phase is £20,000 and another’s is £8,000, don’t ask which is better value. Ask what each agency means by ‘build.’ Does it include content population? URL redirects from the old site? Performance testing? Staff training? Accessibility compliance to WCAG 2.2 AA?
When the phases are broken out, the 5x gap usually collapses into a series of smaller, explainable differences. One agency includes three months of post-launch support; another doesn’t. One prices accessibility compliance; another hasn’t mentioned it. One includes a content migration of 400 pages; another has assumed you’ll handle content yourself.
The quote that looks like a bargain at proposal stage sometimes turns out to be a partial quote. The work it excluded still needs doing. You’ll either do it yourself, pay the same agency to bolt it on later, or pay a different agency to fix it. All three cost more than having it in the original scope.
None of this means the expensive quote is always the right one. Sometimes the £40,000 proposal is genuinely over-specced for a project that needs £15,000 of work done well. Sometimes the £8,000 quote is a smart, efficient agency that builds quickly on a platform it knows inside out. The gap tells you something is different. Your job is to work out what.
