Can anyone with results help me understand the profitability?

For $3000 today I can purchase 0.154 BTC or 20000 GH/s on Hashflare which according to the mining profit calculators should amount to over 1BTC in one year. So what am I missing?
I read a lot of posts saying I will be lucky to break even. Does that mean the calculators are way off and I will not even mine the 0.154 BTC I can just purchase for that $3K today?