I don't see where hashing sellers are really losing much. Nicehash's fees are maybe 1-2% higher than a normal pool but with nicehash you auto switch to the most profitable algo on the market. For instance when Electroneum launched recently it was extremely profitable to mine, and without having to know anything about it, deal with faulty pools or anything, I got extra profit on the spot for about three days that more than made up for their extra fee %.