I went for 30%, and to be honest, I think that's being generous.
I can buy an Infinity character of very close (if not equal) to GW quality sculpting for AU$12.50, where to get the analogue for 40k will set me back $20-25 if I'm lucky. The Infinity core book was roughly the same price as my Eldar Codex, full colour, equivalent quality and over double the page count.
To buy a playable force for Infinity, it cost me $50.00 (unpainted), to do the same for 40k? Easily $300.00+
GW like to use the tagline that they were the best quality miniature wargame figures in the world. That used to be true, back in the days of things like Warzone and even when War Machine first came out. However, Malifaux, Infinity and a slew of other games have proven that GW-quality figures can be made at a fraction of the GW asking price, and those games frequently have the added advantage of (in my opinion) a vastly more interesting ruleset (because let's face it, 40k hasn't changed dramatically since 3rd Ed, and could really do with a major overhaul). All 40k and fantasy have going for them at the moment is fluff, and I can get my fix of that from either computer games or the Fantasy Flight RPGs (which though expensive in their own right, are a far cheaper hobby then the mini games).
So yeah, if GW want my custom, they'd best decide to be competitive, because to be blunt they aren't anywhere near it right now. Unfortunately, I fear they'll hang themselves first. I just hope the IP goes to someone with some sense.