I don't know how you guys do it, but I don't know any places, where you can sell or buy bitcoin for a good rate. If you go to localbitcoins or other places, where you can buy btc, the price is usually higher, than trading price plus you have to pay fees, if you buy with fiat and they are not so low.. usually 10 or 15%, sometimes even higher. And if you want to sell, the price is lower than the trading one. So basically the price has to change 20% up or higher to make some profit with selling and rebuying.