I haven't been able to find out any idea of what a PT who starts their own practice can expect to make.
That's because how much a PT earns in private practice varies considerably. But the only way to really break the 100k salary mark is to either go into a successful private practice, get an administrative faculty position, or enter a medical management position.
So, generally speaking, if you do well in private practice, you can make more than 100k for sure. Again, this depends on a lot of factors, e.g. location, reimbursement, number of visits, etc.