The 5950X is now pretty midrange when it comes to some desktop benchmarks, but mine is still serving me well and I don't feel I'm hitting the limits of the CPU. If I were shopping now I'd certainly find that price appealing for what it offers. I'm not considering Intel these days, but the price premium on latest-generation AMD CPUs is high.
It's one of the latest my mobo can handle AFAIK, and i like to maximize my hardware for longevity (one of the reasons i prefer AMD over Intel, their CPU generations span multiple sockets).
Yes, I went up to a 5950x a while back from a 3600 for the same reason: it was the best CPU I could get without upgrading motherboard and RAM. And I hardly ever play games. Looking at the performance benchmarks it seems the X3D stuff actually slows down non-gaming workloads a bit (perhaps because it increases temperatures), so I don't feel the need to chase after that tech.