By Ted Gibson — RippleEffect
For a mid-market UK brand most Amazon agency retainers land between £1,500 and £5,000 a month, with smaller accounts nearer £500 to £1,500 and US full-service agencies commonly quoting $1,500 to $5,000 a month or more. Read those ranges with some suspicion, because almost every published figure in this market comes from an agency describing its own market. The more useful question is not what the number is but which of three structures it sits inside, since each one bills you for something different.
The three ways agencies charge
A percentage of ad spend, usually 10% to 20%, is the most common model and the one whose incentive points furthest from yours: the agency earns more by spending more, whether or not the spend is efficient. If you take this model, the number to negotiate is not the percentage but what happens when advertising should be cut.
A flat retainer is predictable and easy to budget, which is why finance teams like it, but it gives the agency no stake in whether you grow. It suits accounts that mostly need maintenance and suits an agency's cash flow better than yours once the account is scaling.
A percentage of revenue, usually 3% to 10%, aligns the two sides better because the agency only earns more when you sell more. The flaw is that a single flat rate on revenue quietly penalises you for scaling, since a brand at £150,000 a month pays three times what it paid at £50,000 for work that has not tripled.
What almost nobody will tell you
Whichever model an agency uses, you usually cannot find out its price without sitting through a discovery call, so your first conversation is a negotiation rather than a diagnosis. The cost guides that do exist are mostly written by agencies about agencies, and their worked examples tend to be hypothetical rather than real clients. We publish ours instead, which makes us one honest data point rather than the whole picture: a catalogue-sized retainer plus commission charged in marginal slices like tax bands, so the effective rate falls as you grow. A 30-SKU brand on one marketplace pays 8.5% of sales at £50,000 a month and 4.3% at £150,000 a month.
What to check before you sign anything
Ask what the fee excludes. Ours never covers advertising spend, content production or Amazon's own fees, all of which you pay directly, so the fee is only ever for the work itself, and an agency that blurs that line is worth a second look. Ask about the one-off fee too, since onboarding or takeover costs are common and rarely advertised.
Then ask what you get before you commit. Every engagement here starts with a free account audit of your listings, campaigns and catalogue, with a prioritised set of first moves. Seeing how an agency thinks about your account is worth more than any range on a pricing page, including this one.