It’s possible to reject the argument that consumers seeing ads is the same as monetary payment.

I'm fine seeing ads. I wouldn't pay commercial rates for the services I use.

I find ads maybe 20% useful and for me that's a good deal.

You have to explain why and how you are rejecting it.

The point of the poster above is that you're ultimately paying for your free email with a Google tax on every carton of milk and every smartphone you buy. That is, if advertising were banned and you had to pay for Gmail, most of your other purchases would be just a little bit cheaper, because they wouldn't be paying for Google ads to support your free email.

And this is just basic finance: the advertising budget has to be paid for somehow, so it is priced into the goods themselves (either through higher prices or lower quality, of course).

True, these services are not and never were free, we pay for them with our data. I would say this is all fairly common knowledge, my parents who are not tech savvy understand this, and I genuinely don't believe people care enough. I know this trade off, my tech savvy friends and acquaintances know this and yet we continue to make this trade off because frankly I don't think many value their personal data at all, and I think that's why we say these services are "free" because we're not trading anything we find particularly valuable.

The problem is that you don't actually know how valuable it is without knowing how it's being used. If your ad-view statistics are used to charge you personally a higher price for a product than someone else who didn't click on the same ads, is that still okay? If they're used to raise your mortgage interest rate, is that still okay? If they're used to sell scam products to old ladies, is that still okay? If they're used to peddle political misinformation to support the election of a fascist, is that still okay? You don't know what tradeoff you're actually making. Maybe you'd think it was okay, maybe not.

Modern companies have become very, very good at making consumers believe they are getting a good deal by trading an obvious benefit for the possibility of a hidden harm. The type of data tracked by internet companies is only one form of this.

I fully agree with you - the practice of price discrimination is illegal under the Robinson-Patman Act and Google should be penalized for violating this law if they have been found to do this. I am only trying to push against the notion that Google (or any company) should be broken up just because they are big. This is the nuance that makes these discussions important IMO

My position is basically that enormous market power is like a ticking time bomb. It's not going to work to try to patch over it with specific prohibitions like the one you mention, because big companies will always find loopholes, use their market power to exploit them, and use their wealth and "too big to fail" status to drag out any attempt to enforce the rules. It is an endless game of whack-a-mole that can never work. It's better to just limit the total power of companies to do anything; doing so will also limit their ability to do harm of any kind.