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.
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.