I've been looking at nicehash.com, and I have seen the buyer and seller section.
For the buyer side, according to my calculations, I just can't see it being a good deal. According to my figures from bitcoinwisdom.com, it seems like I'd earn about 80% of the BTC that I spend on buying mining time. If that is correct, then why would anyone ever be a buyer? Is it only a good deal when buying in large amounts of hash power and time?
I think people looking to make more than they spend on nicehash are mining altcoins in hopes that the price of that coin jumps a lot. With all the new coins constantly being released people try and get in early to mine before the pump so they can dump before everyone else does. Otherwise it makes no sense to spend x amount of bitcoin to make less bitcoin.