Out of interest the other day I found my receipt for my 2010 cMP which I bought just over a year later for 1400 pounds and according to the site below was 2800 brand new -
https://everymac.com/systems/apple/...re-2.4-mid-2010-westmere-specs.html#macspecs3
If the nMP had the same residuals then I might hope to grab one for around 2.5k in around 2 years ? Any thoughts ?
When you refer to the nMP are you referring to the 6,1 or the 7,1? I ask because the nMP has historically been applicable to the 6,1 however I can see how it could easily, and appropriately, be applied to the 7,1.
If you're referring to the 7,1 I think its residual will depend on what Apple does in the future. It's my opinion the 4,1 and 5,1 Mac Pros retained their value because of the drastic change Apple made with the 6,1 and the neglect the 6,1 saw over six years. Thus the 4,1 and 5,1 were coveted and prices remained higher than I would normally have expected.
If Apple beings a process of steady upgrades to the Mac Pro line then the 7,1 may not retain its value as long as the 4,1, and 5,1 did by the sheer nature of it becoming obsolete faster (the 4,1 and 5,1 become obsolete due to changes in technology but since Apple didn't incorporate those changes into updated systems Mac users were forced to continue using them). Take the 1,1 and 2,1 as an example. Once Apple announced no future OS support after Lion prices of those systems fell through the floor. Something similar happened to the 3,1. The 4,1 became less desirable than the 5,1 when Apple announced Mojave would not, by default, install on it (though an flash update solved that issue and therefore it didn't see a significant falloff in price).
As for whether the 7,1 is a good buy that's subjective but if you buy one today and use it for 10 years then it's not expensive at all. Initial outlay may be higher but you may get solid value out of it. Especially if it provides more "productive" work than the cMP did during its lifetime.