Normalise scope before you normalise price
The first mistake is comparing monthly fees before confirming the proposals cover the same work. One agency's retainer might include content and listing optimisation, another might quote that as a separate line item. Build a simple table listing every workstream, meaning advertising, content, operations, strategy, reporting, and mark which proposal includes each one inside the base fee versus as an add on.
Once scope is normalised, the price comparison becomes meaningful. A higher monthly fee that includes operations and content is frequently better value than a lower fee that only covers advertising and leaves the rest for you to handle or pay for separately.
Pay specific attention to what happens in month one versus ongoing months. Some proposals bundle a substantial setup or audit fee into the first month's rate in a way that makes the ongoing rate look higher than it actually is once amortised. Ask each agency to break out onboarding or audit costs separately from the steady state retainer.
Read the pricing model for its incentive, not just its number
Percentage of ad spend rewards an agency for spending more, which is fine while scaling and can become misaligned the moment the correct move is to pull back spend and fix conversion first. Percentage of revenue aligns better in principle but can reward an agency for revenue it had little to do with, particularly around seasonal peaks. Flat retainers put the burden on you to define scope precisely but survive a decision to cut spend without the agency's incentive working against that decision.
None of the three models is objectively correct. The question is whether the incentive it creates matches what you actually need from the engagement right now. A brand in aggressive growth mode may be fine with a spend based model. A brand focused on protecting margin on an already large account usually is not.
Pressure test the case studies the same way across every proposal
Apply one standard to every case study you are shown: what was the baseline revenue, was the category growing independently of the agency's work, did new products launch during the period, and how much did ad spend increase alongside the growth being claimed. Agencies with real results will give you this context without resistance. Vague or defensive answers are the signal, not the growth percentage itself.
Ask each agency for one reference client in a comparable category and revenue range to yours, and ask that reference specifically about the worst month of the engagement rather than the best. How an agency communicated during a bad month tells you more about the actual working relationship than any growth number.
Check whether the case study reflects the team that would actually work on your account. It is common for a case study to feature the agency's most senior talent while your account would be staffed by someone more junior. Ask directly who would be assigned and confirm that person's track record specifically.
Contract terms that decide whether you regret it later
Compare notice periods across every proposal. A long lock-in with a short notice window is the single clause most likely to cause regret if the relationship does not work out, and it is worth negotiating even against an agency you feel confident about.
Confirm who owns advertising data, creative assets and account access if you leave. The right answer is that you retain full ownership and the agency's role is scoped access that you can revoke, not a structure where leaving means starting from zero.
Get exclusivity clauses in writing if they exist. Some agencies require exclusivity across all your Amazon markets or all your advertising channels, which can be reasonable or can box you in unnecessarily depending on how it is worded. Read this section closely rather than skimming it.
Frequently Asked Questions
Three is generally enough to see real variation in approach without the comparison becoming unmanageable. Fewer than three and you have no real basis for comparison. More than four or five tends to produce diminishing returns and mostly costs you time across repeated discovery calls.
Not without normalising scope first. A cheaper proposal that excludes operations, content or reporting frequently costs more once you account for what you will need to source separately or handle yourself. Compare total cost for equivalent scope, not the headline monthly figure.
This varies with account complexity, catalogue size and how much structural work the account needs, so there is no universal benchmark. The important thing is that it is quoted separately from the ongoing retainer so you can see clearly what you are paying for in month one versus month six onward.
Some agencies offer this and some do not, and it is a reasonable thing to ask about even if it is not standard practice for that agency. A shorter initial term with clearly defined success criteria can work as a lower risk alternative if a full trial period is not offered.
Ask for the baseline revenue, category growth trend, whether new products launched in the period, and the change in ad spend alongside the growth claimed. A number without that context is not verifiable, and an agency confident in its results will readily provide it.