Profit-seeking has led to lots of progress in this world, but its record is decidedly mixed. Keep your eyes open.
This is not about the total gain of both sides: Almost every transaction is positive sum. However; why should I simply accept the 90/10 distribution of the excess in their favor when I can aim for a favorable distribution for myself too?
And I'm also confused by your talk about favorable distribution. Isn't seeing ads relevant to your interests better than seeing ads unrelated to your interests? The problem with targeted tracking isn't that it's targeted, it's that it relies on information whose collection is a privacy violation. But when we're talking about a company that you've already voluntarily given massive amounts of behavioral data to, then you've voluntarily given up your privacy so there's no violation going on.
> Those behavior changes are intended to make you give the buyer more money than they paid.
That is literally the goal of every merchant everywhere. They need to sell stuff for more than they paid, otherwise they don't make money. And there's absolutely nothing wrong with this. They aren't forcing you to buy things, their buyers think that what they're selling is worth the amount they're selling it for (or they wouldn't buy it). This is the fundamental basis on which all commerce everywhere operates.
As for the Las Vegas angle, that's complete bullshit. Gambling operates very differently from commerce, and there's really no basis to make this comparison at all. Seeing an ad that's relevant to your interests has pretty much nothing in common with gambling beyond the fact that both of them involve money at some point.