Okay, how about the lesser of 10% of the patent owner's monthly income or $10,000 to file? From there, it would be another $10K for the first 5 years, and $50K for 3 5-year extensions? Then the filing can be modest.. and upon approval, will be about the same to cover 5 years, and have to re-up at a higher cost.. assuming the patent is actually worth keeping active by then.