I have to second John's comment above. I signed up with MedFx with the understanding that it would roll into AC when the time came. The price is the same.
Most clearinghouse fees are anything from $50-100/month and then there are additional fees for software maintenance. This is WAY less than 5-9% most billing systems charge, but then again, you are doing the work.
Yes, I would have liked something half this price, but sometimes you get what you pay for.