@hera kitty I come down hard on things that have the potential to be negative for the field or the person. It's much better for you to think of me as a jerk, than for you to get fired from your job. It's also much better for everyone, if the field shows they understand basic business stuff.
1) The term "fee splitting", in general, has a very specific legal meaning which refers to payments made to a referral sources from monies earned from those referrals. It's usually a federal crime. For example, if I owned a law firm, and sent all of my car wreck cases to you, but required you to send me 10% of the insurance collections for those patients care; that would be fee splitting. Owning a practice, hiring contractors to see patients, and paying them a percent of what they collect is completely legal, and is not fee splitting. Now imagine you're a business owner, and an new employee immediately accuses you of a federal crime. Wouldn't you think that the easiest way to fix that is to terminate their contract? I would.
2) Fairness matters little in business. You are free to enter into almost any contract you want.
3) You are being paid 70% because that is what the practice owner thinks is manageable. That 30% may cover overhead, but it also cover his/her profit margins. As an employer, he/she is entitled to earn profits. Because you are an employee, and not a partner, you are not in a position to question the owner's moves, and it would likley be a bad idea to do so.