£8-10 For a top-game I'm playing intensely.

£3-5 For a casual game, especially if no initial purchase required.

I wouldn't ever pay a fee for a AAA game I'm not going to playing intensively, or more than one AAA subscription at a time.

I cannot really say what my upper limit would be, but if a game of extraordinary pedigree and quality were to be released charging £15-20 say I'd probably pay... for the month or two it takes to complete the content, then I'd be getting out of there!