By offering to pay you've identified as someone who pays for things making you more valuable to google, thereby increasing what you should pay to Google if you

By offering to pay you've identified as someone who pays for things making you more valuable to google, thereby increasing what you should pay to Google if you want to go ad free. Then google could offer a bidding war to advertisers to pay more than what your paying to get ads back. Then you have to pay more than that. Until an equilibrium is reached.