Hi,I got some GHS at 0.0089BTC/ GHs serveral days ago.But today I find the price is 0.0075BTC/GHs, So I want to know what rules used to change the price by you ? 
prices change once in awhile. usually at diff change. but recently also when new hardware is added (I think)
don't be sad... my first Ghs cost almost double the current price