You could just as logically say that if the user has spent money to remove advertising, then they now have less money and are less valuable to advertise for.
Thank you for the laugh.
While this may be true on an individual level, it’s wildly not true in aggregate.
The first dollar is hardest to get. Once someone has shown a propensity to spend on pretty much anything, they become much more valuable as an advertising target.
That's like thinking that a girl is likely to sleep with everybody because she has a boyfriend. "She's already sleeping with one guy, so why shouldn't she sleep with everybody?".
Of course your current customers are excellent targets for your own upsells and your other products. But not much else.