I've been very happy with coinbase's system for the opposite reason.  They were (at least when I was trading) matching in near-real time bitstamp prices and bitstamp would have these large swings up or down, usually corresponding to low volume ... lower than what I would buy at coinbase.  Working between the two, I got 5% excess profit 2 times last year, and someone had to absorb that loss because the volume I got at a low (or high) price was more than the volume that transpired on bistamp.  So coinbase and/or bitstamp had to absorb that loss.  Conversely when you lose on trades, one or both of them accidentally gain.  I was looking for it because after reading about their agreement with bitstamp, I wondered how they were going to be fair to everyone and keep their profit always at 1%.  The answer is that they can't.  They have to gain and lose on trades accidentally (beyond what their programming and agreement is able to deal with).  It is not possible for them to give the exact price on bistamp because they are not directly on the exchange.  This is why coinbase has a limit on trades. You've got 50 coins per day to use, if you want to "work the system" at someone's loss, you've got to make the right guess or be the loser yourself.  You can't do a bot at coinbase, so the competition in that type of "trading" environment is diffrerent. There would have to be a serious merger of the trades to get exactly 1% profit on every trade.  I trust they are trying to be as fair to everyone as possible.