You are correct! I think Athena is the only one that charges a percentage of revenue instead of a flat fee. I have seen the contract though and was shocked to find out.
I wonder how this works in states that prohibit fee splitting arrangements?
So I was curious and decided to see what I could learn. Apparently you can't get Athena EHR w/out utilizing THEIR billing services, so be aware of that if you are being hired by or taking on a client that has them. They basically contract with the doctor for their billing services and in exchange for their 4-7% of revenue the practice get to use their EHR. I found this review which spells it out: http://www.curemd.com/EHR-vendor-pricing-comparison.pdf