because i am a bit newbiew..... can anyone explain me the average BTC you can make per day?

Hello,
i am thinking of buying a BitForce Jalapeno,i've seen some good reviews about it.But can anyone tell me if its really worth to buy it? will i make my money back? right now i produce 40mhashes/sec with my GPU... with the Jalapeno how much BTC i can produce per day? (ok i know after 1 year everything will be screwed with these rigs...) so if i make it fast i can make some money from this... so can anyone tell me a serious opinion about it???
Thanks !!!