Sure, everything that's not explicitly prohibited is permitted, and wealth is not one of those very few things prohibited for discrimination. You're free to have a club that only admits billionaires or offer a discount that applies only to people below a certain amount of income.
The example on ability to repay is closely related to discrimination by pure wealth, but there are businesses with even more straightforward criteria, e.g. financial services that are offered only to individuals with net worth above a certain (quite large) amount, and having less money than that automatically disqualifies you from that service even if you were able and willing to pay the involved fees.
> Sure, everything that's not explicitly prohibited is permitted
That was not the issue. The question was whether it is desirable.
Personally it leaves a bad taste. It reminds me of a fashion brand that doesn't sell to obese people (can't remember the name but it was in a documentary).
