A big part of the problem with these scraping operations is how poorly implemented they are. They can get a lot cheaper gains by simply cleaning up how they operate, to not redundantly fetch the same documents hundreds of times, and so on.

Regardless of how they solve the challenges, creating an incentive to be efficient is a victory in itself. GPUs aren't cheap either, especially not if you're renting them via a browser farm.

Anubis et al. are also looking into alternative algorithms. There seems to be consensus that SHA-256 PoW is not appropriate