I would suggest it is not so much related to level of income, but rather knowledge of money management. The choice of buying more assets than liabilities is a basic, reliable (although frequently dull) way of acquiring wealth.

I am reminded of frequent stories of individuals with large incomes still being relatively poor - Doctors, Lawyers, etc. purchasing ever larger houses, ever more luxurious automobiles, etc. (all liabilities).

Or, as one individual who like to get peoples' attention puts it: "It's not how much money you make, but how much you keep."