CeX are OK for older computer parts (apart from when they get it wrong), bit like eBay but only same day walk in walk out service. My local shop has a beat up SNES in for £140, I bet they only gave the seller a tiny fraction of that. It's like when you trade in a totally mint 15 year old car and the dealer gives you pennies for it "cos it's old init" but then advertises and sells it for a lot more than your average 15 year old car "cos it's in mint condition".
The server RAM I returned is no doubt back in their pile for sale as according to the website my local shop has one in stock ever since I returned it yet when I got it exchanged they only had one so should have been zero.