A workaround for an Amazon PPC UI limitation: placement multipliers (Top of Search, Rest of Search, Product Pages) can only be raised, never lowered below the campaign's base keyword bids.
To net-decrease weaker placements while still raising a strong one: go to the Placements tab and increase the multiplier for the well-performing placement (e.g., Top of Search +10%), then separately go into the campaign's keyword bids and lower every individual keyword's base bid by that same percentage. The raised placement multiplier cancels the base-bid cut for that placement, while every other placement nets lower.
A manual-arithmetic bypass for a gap in Amazon's placement controls, used during the bid-tuning phase that follows the initial aggressive launch bidding.
Direct quote on the constraint driving this workaround: "the problem is how this bid adjustment works is you can only increase your bids by a percentage that you set here. You can't decrease it" — hence raising the placement multiplier while simultaneously lowering every keyword's base bid by the same percentage, netting a placement-specific effective decrease.
Example: if Rest of Search is running a high ACoS while Top of Search converts well, raise the Top of Search Placement Bid Adjustments (Top of Search / Rest of Search / Product Pages) multiplier while simultaneously lowering every keyword's base bid by that same percentage. Top of Search's effective bid stays unchanged (raised multiplier cancels the base-bid cut) while Rest of Search and Product Pages get cheaper, since they don't have a matching multiplier to compensate. Apply this as one global change before touching individual keyword bids.
Because Amazon's placement bid adjustments can only ever raise a bid by a percentage (never lower one), effectively lowering a weak placement's relative bid means: raise the adjustment on the strong placement, and simultaneously lower every keyword's base bid across the whole campaign by that same percentage. Net effect: the strong placement's real bid is unchanged, every other placement's real bid drops.
Из тем: Unsorted, PPC Campaign Structure & Bidding