Dynamic bidding (down only / up and down / fixed)

Amazon applies this campaign-level setting in every individual auction. Current documentation says down only may decrease bids by up to 100% for all placements, up and down may increase or decrease by up to 100% for all placements, and fixed uses your exact bid with no automated adjustment; the strategies page's own example is a $1.00 bid going to $2.00. But it runs on top of placement adjustments, not instead of them: the bid adjustments page works $1.00 up to $1.50 with a 50% top-of-search adjustment, then says up and down can push that to $3.00. Rule-based bidding sits alongside as its own strategy, raising bids up to 5 times your adjusted bid toward a ROAS guardrail Amazon says it does not guarantee hitting.

The console shows a bid box, never your real maximum CPC. Placement, audience and video modifiers compound on the running total, capped at a combined 900% increase — 10x base bid — after which dynamic bidding applies to the adjusted number. Multiply the two ceilings and $1.00 implies roughly $20, but that is arithmetic, not documentation: Amazon publishes no such figure. One trap: the +100% top of search, +50% elsewhere split most operators still model was Amazon's own older wording, still live on Amazon's author's guide to Sponsored Products, so product-page exposure is double what the old rule assumes. And down only is a bid cap, not a spend or ACoS cap: operators widely report it drifts the impression mix toward cheaper, worse inventory, though Amazon documents nothing about that.