I never saw profitable mining contracts. It's scam. 
I dont know if they really are scamming you. Use that word wisely. You know exactly what you are buying, the fees you are paying and the risk involved. Thats not a scam, its just bad judgement on an investor.
Yes, you're right. But they show you profitability, they make fake calculators which calculates thousands of dollars you will earn. But in fact it's all fake.
that by definition would be a scam (deceptive and misleading)
While Investing in mining, understanding the difficulty is more important (given it raises every fortnight for BTC)...if u are looking for complete returns in short term then it's a strict no...even if ur buying contracts or mining on ur own... it may take long time...depending on ur hashing speed to break even ur investments...may b months to come.. since i have seen many people asking the same question...how many days it would take to earn my investment back...which doesn't happen unless u are trading ur mining power..
Let sites/forums not fool u...use ur wise judgement before doing it..ask as many people as u can...on different forums...