No he actually can make profits with small amounts too. It only depends on the way he uses. I am aware of people trading that way but directly. For example, $50 = 0,0043 BTC. I will send to my client that amount using a wallet that allows me to select fees (satoshi/byte) so that client might wait long to get his funds (not necessarily of course). Or else, I will buy those 0,0043 BTC for him with $53 (or $50+fees) if he wants his funds faster.