Yes I fully agree with the prices being steep, that's why I wondered if anyone could point me in some other directions aswell
When you speak of Amazon, do you mean other people selling stuff through amazon? I've not really investigated Amazon from that perspective. I normally go about checking ebay.co.uk but most of the stuff there is quite pricey aswell
Yes, Amazon is basically a large collection of small shops, even when you buy new stuff it very rarely comes from Amazon itself. Think of it as an aircraft hangar full of individual stalls, yes it is possible to get burned but honestly to the scale of it actually mattering (Eg a game described as "Very Good" when in reality it's scratched to bejesus) is very tiny.
Admittedly the majority of my purchases have been 5th and 6th Generation, with the odd old PC or Gameboy1 titles, but there also some old Home Computer (80's) games which are available though i've not yet explored.
If you're a serious collector for old cartridge-based games then perhaps there are better places to be looking, but if you just want the games in decent condition then it's kinda crazy to pay any more for them.