eCPM (effective cost per thousand impressions)

Amazon prices ads on incompatible bases. CPC bills Sponsored Products, Sponsored Brands "drive page visits", and Sponsored Display — now labeled just "Display" in Amazon's own help. vCPM bills Sponsored Brands "grow brand impression share" and Display reach; Streaming TV and most Amazon DSP buys are impression-priced. The published US vCPM minimum bids — $1 for Display, $8 for a Sponsored Brands image and $12 for the video version, all varying by marketplace — mean nothing beside a click bid until you convert both. eCPM is that conversion: spend ÷ impressions × 1,000, the arithmetic Amazon states on the API benchmarks cpm column. For click-billed campaigns, eCPM = CPC × CTR × 1,000, with CTR as a decimal, not the percentage the console shows.

Amazon already reports a price per thousand in two places — a vCPM column (spend ÷ viewable impressions) on the vCPM-billed goals, and cpm with P25/P50/P75 peer percentiles in the benchmarks report. It reports none for CPC-billed campaigns, and the v3 reporting API exposes no vCPM column, only a costType dimension, so API-driven stacks derive it. eCPM is the only conversion-free view of what you pay for distribution, where ACOS and ROAS blend price with conversion rate and a strong conversion week hides rising prices. Two traps: hold one denominator, since total impressions is the only one every cost type reports; and never compare ROAS across cost types, because the v3 docs are explicit that vCPM sales include click- and view-attributed sales while CPC sales are click-attributed only.