If they're half as likely to convert but four times wealthier, does it matter?

Four times wealthier does not mean they'll spend four times more on your products.

The answer here isn't really obvious, but I'd suspect that in many cases this is not a very attractive demographic to advertise to.

They should have used the term more valuable not more wealthy, their point is generally cogent.

On the wealthy side, you don't need to be that rich to pay not to get ads.

Fair enough, but keep in mind that many Americans are just not wealthy enough for a lot of advertised products; a luxury car ad, for example, is mostly useless if it's shown to people making < $60k a year.

This demographic is inherently attractive simply because they can spend money.