Most FX brokers charge customers fractions of a basis points per trade, and they run a legit operation that often has high costs for compliance, customer support phone numbers active 'round-the-clock, efficient and reliable IT infrastructure, substantial banking costs for account management and more.
Compare this with the largest bitcoin exchange by volume, MtGox. They offer a terribly unreliable service, slow customer support, high exposure to counterparty risk for the funds you entrust them with, have to comply with fewer regulations (and recent events suggest they fail to do even that) and yet charge two orders of magnitude more than any competitive retail FX broker.
I understand that there is still little competition in the space where they operate, but the situation has been lasting for a while and I am wondering if there is any good reason why things should remain this bad. Is there perhaps something structural that I am not seeing?