Anecdote: I have logged 3700 hours on oDesk (before they merged with Elance into Upwork) for about 20 clients. About half of that was for two biggest clients. I

Anecdote: I have logged 3700 hours on oDesk (before they merged with Elance into Upwork) for about 20 clients. About half of that was for two biggest clients. I think there's power distribution in play. While browsing Ruby on Rails jobs I often saw client profiles with more $50.000 spent. Yes they have some big fish to cater for. Those clients (and freelancers like me) might consider higher commission for first 2-3 months of work (to reach $10.000 threshold) as kind of recruitment cost. Then, 5% commission is acceptable for payment and accounting automation.