A placement modifier is a percentage increase applied to your bid for a specific ad placement — Top of Search, Product Pages, or Rest of Search. Amazon allows increases of up to 900%, applied on top of your keyword bid, so a 50% modifier turns a $1.00 bid into $1.50 for that placement. Modifiers only go upwards, so the way to spend less in a weak placement is to lower the base bid and raise the modifier on the placement that performs.
Why placements differ so much
Top of Search usually costs more per click and often converts better, because it sits above the fold on a page of active search intent. Whether the premium is justified is an account-level question, not a universal one.
Product Pages traffic behaves differently — the shopper is already looking at something specific, so relevance to that listing matters more than keyword relevance. It frequently carries hidden waste in accounts that have never reviewed placement data.
How it stacks with bid strategy
The placement modifier is applied to your bid first, and the campaign bid strategy adjusts from there. With dynamic bids up and down, a large modifier and an aggressive strategy can compound into a considerably higher final bid than the number you typed.
Change one at a time, and give each change enough clicks to read before making the next.
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