I have definitely seen job postings that were so detailed and narrow that they couldn't possibly find anyone "qualified". They were clearly making it so that it would be easier to claim that nobody in the country was qualified.

But I will say that the only people I have met that are here on H1-B have been uniquely qualified for their position. Such as, they invented a way to scale a given chemical manufacturing process, and they were developing it further.

But I got the impression that they were not particularly well paid like I would expect an American in the same position to be.