The classical rate determination methods for REAL insurance programs determine premiums based on many things: age, sex, lifestyle (smoking for example). Income for income's sake isn't a variable (unless by virtue of having money it has been proven you live longer).
Because someone has 'more' money is no reason to charge them more than someone with 'less' money simply because they can afford it. Extend that line of thinking to the hot dog line at a ball game, because it makes just about as much sense.
This flawed logic of 'we'll go bankrupt' or 'it's only right they should pay more, because they have it'is rooted in envy, jealousy and laziness.
The only plan that is 'fair' is 'equal' treatment. Income-based rates are neither.
I assumed the program is structured roughly on the same principle as the progressive income tax.