Why are there such huge differences between commissions on different exchanges? Why are there such huge differences between the commissions applied by sites like Bitstamp.org (0.5-1%) and other sites (I have seen 5-10% fees)?
It varies from exchange to exchange because people running exchange are different with different thinking. Me and my brother runs a website where we sell coins in exchange of USD(we are not a exchange anyway just small dealer) we do charge some fees but the difference here is my brother will charge a customer upto 20% higher than actual rate on the other hand(u have different fingers) I charge only that amount which is reasonable.