Good reason to retain my 40 year old Crime of the Century UHQR?

Playpen
I also have the "standard" MOFI release which is more like a $25 album but the SQ is off the charts.
This is still one of my goto albums for testing changes made in my system.

I am not sure how much better the UHQR version can get tbh, certainly not 20 times better.

Good luck to the OP whatever he decides as it is a very nice and valuable record indeed!

Seems like an easy decision if you're not a collector, but an "enjoyer". If you don't listen to it (much), then you can always get another version for a lot less and casual listening. The going rate could buy a lot of software you'll enjoy.

Don't know what country you're in, but a quick check on Discogs shows 4 for sale, the only US seller wants $750 (NM). You could always offer it there for top dollar, and if somebody bites congratulations!

I have an original Mofi and a 1/2 speed Canadian Audiophile  of COTC and both sound superb. 
Sell it,buy a used mint MOFI copy and spend the 450 left on music or whatever. You will still have an excellent recording of COTC to turn too.