Looking around ebay at parts here what I've found
CPU: Seems to be going for anywhere between 350-500 CAD. However a comparable Ryzen 3600 is only 236 and a better Ryzen 3700 is 400 CAD.
Mobo: that's a tough one to price, again used prices seem to be in the 200+ range but the only ones getting bids are around 100, so realistically expect 100-150 CAD for it at best
Cooler: I wouldn't bother adding it to the cost and if you part out your system toss it in with the CPU/Mobo as a combo.
GPU: 1080ti is still a good card and seems to be going for around 450-650CAD. with the ones in the 400-500 range actually getting bids. If you expand out to the US though there are some in 300 range also since we have a far larger used market here and plenty of people will just ship it up North.
RAM: Maybe 65 CAD, probably alittle less
SSD: 80-100 CAD but there are cheaper ones in the US four roughly 70 CAD so again it would be something easy to ship up to Canada.
HDD: Are dirt cheap new and used these days, I know here in the US you can get used 2TB HDDs for 20 or 30 bucks, sometimes even cheaper if you find someplace selling old server stuff.
PSU: Another tough one to sell since many people wont know how many surges its been subjected to, how long its been left one etc. Again I would maybe add 50CAD to the cost if
These are just what the parts are going for individually, you can look around ebay and Facebook marketplace for comparable whole systems and figure out how much its worth, but again remember alot of PC prices are inflated waaaaay to high so make sure to keep an eye on things that are actually selling.