I fifure it has to be more than 10%. Thats just a guess though. And the more I think about it the more I think it will be based on the specific item rather than a straight discount. They are already at the bottom price on bulbs for instance, and to take 10% or more off that theyd be making nothing. Same thing with their base rock, it's pretty cheap already.
i was also thinking it could be the "lowest" price thats sometimes listed when you buy multiples. On bulbs if you buy more than 4 you get a buck or so off each one, which in my case would be nice as I need 12 bulbs!
And in the worst case scenario, and the prices arent good enough, nothing is lost and we get to learn how it works. We are not commited to buying anything at all. But i'm sure a few things will be too good to pass up.