To provide equal opportunity, Google redesigned the advertising platform as a price comparison service (CSS) and opened it for external price comparison platforms – the so-called Google CSS Partners.
Google`s own price comparioson was re-named to Google Shopping Europe (GSE) and also functions as CSS (“by Google”), participates in the bidding auction like any other price comparison platforms and competes with other CSSs that place bids on behalf of merchants. To run its own comparison shopping service in compliance with the EU rules GSE must work profitable independently.
To do so GSE keeps about 20% of a merchants maxCPC bid as a margin. Therefore, bids are reduced by about 20%, if they advertise through Google Shopping Europe. On the other hand, if a merchant uses a Google CSS Partner, the margin is completely deducted.
In conclusion, these efforts brought external price comparison services into a fair competition with Google own service.