There’s some brilliant value rims out there- £18 for a WTB Stryker XC rim at CRC (the weights are wrong btw) or £28 for a KOM i23, frinstance. Set of decent hubs spoked with Lasers would give a reliable XC wheel (not race-day XC, everyday XC) for a good low price.
New wheels don’t seem to be such a good buy, I guess because they just stopped doing them, and they became a 650b wheel and a discounted rim instead. But light, used 26 parts are pretty cheap (it seems like tougher 26 parts are holding a bit more value). Roval Controls and Traversees can be a good one, though you’ve got to be sure not to get the crappy OEM versions, and they’re awkward for parts- but you see them going past for £100 sometimes and that’s silly for what you get.