I love getting a bargain and rarely pay over £20 - the cheaper the better!
I've just got back into gaming after a couple of years off, so I've paid a bit more for some DS games that have become harder to find. I've also bought a few cheap preowned games from Cex, That's Entertainment and eBay.
Generally though I keep an eye on HUKD and other forums to spot the cheap games. I've got a massive backlog so I can wait to pick up games when they've dropped in price.