AMD Hawaii GPUs in their professional variant (FirePro), which were cheap, unlike the "datacenter" GPUs of today, and the more recent Radeon VII had much better FP64 performance per $ than GTX Titan.

Moreover, there were claims that the memory errors on GTX Titan were quite frequent. On graphics applications memory errors seldom matter, but if you have to do a computation twice to be certain that there were no memory errors affecting the results, that removes much of the performance advantage of a GPU.

Fair enough. I did not know about these. It's hard to find reliable MSRP for them today, though. Given the era, market segment, and the competition, I'd estimate $1500-2000. It's not clear to me they were on consumer store shelves, either, whereas the GTX Titan was.

A cheap GPU ten-plus years ago was $200-300. That GPU either had no FP64 units at all, or had them "crippled" just like today. What happened between then and now is that the $1k+ market segment became the $10k+ market segment (and the $200+ market segment became the $500+ market segment). That sucks, and nVidia and AMD are absolutely milking their customers for all they're worth, but nothing really got newly "crippled" along the way.