Google already has too much info from email, location tracking, and search history. Getting into bank accounts is too much. It would let them know exactly how effective advertising is since they would see how money is spent and they already know what advertisements they show you. Sorry, but no. Hard pass from me.
Brynn Bardacke (Google Pay Senior Director) stated publicly that: 1) Google Pay will never sell your information. 2) Specifically, Google Pay will never sell your transaction history to third parties 3) Or share it with the rest of Google for targeting ads. Source: https://youtu.be/A2hL32k7Y0I?t=934
So he's being very misleading here, likely deliberately. They don't directly share it with the rest of Google, but indirectly your Google Pay data is still laundered through shady Mastercard deals to Google's ad behemoth anyway.
Google Pay -> Data laundered through Mastercard -> Google Ads