It really depends on what you need it for and what sort of deal you can get.
I purchased a used 2019 Mac Pro about two weeks ago with the following specs:
16-Core CPU
96GB RAM
2TB SSD
580X GPU
For $2,000. I replaced the 580X with a W6600X for another $630 (I qualify for edu discount).
So, after tax and shipping, it worked out to about $2,800 in U.S. currency.
View attachment 2075118
How did I manage this? Ebay search error. The seller is a computer store with thousands of items up for sale, the starting bid was $2,000, but it didn't show up when searching for "2019 Mac Pro", and they never bothered to check. Hence, I was the only bidder. Currently, this configuration is about $10,000 on Apple's website brand new.
So, I got extremely lucky, and I didn't really believe it until I had it on my computer desk. It's in perfect condition, nary a scratch. Comparatively, the 16-core CPU upgrade alone is $2,000. Given my good fortune, and the longevity of previous Mac Pro models, I fully intend to make this thing last for as long as possible.
Which I suppose is the question, the Mac Pro is on the cusp of being replaced, and it's yet to be determined what form it will take. It all depends on what you consider to be the right price and how different the Apple Silicon Mac Pro will be compared to its predecessors. I value x86 compatibility, this is probably the last of the Xeons, so this was an obvious purchase for me at a stupid low price.