>There's probably an upper cap for this effect, but I'd argue that 99% of us will never reach that.
I think that you have diminishing returns on this as you earn more money... I don't think it's so much a hard cut off. The 'freedom' difference between being dependent on family for rent and being able to support yourself is larger, in my opinion, than the freedom difference between owning your home and owning a block of apartments.
In my mind, if you can make a programmers wage, and you feel like you can easily get another job if fired? you have a pretty large degree of freedom.
I also think that 'job security' or, perhaps 'perceived income security' has as much to do with this freedom as does the amount you earn. If you feel like your boss can fire you at any time, and if you feel like you can't easily get a new job? you... are going to feel rather less free than someone who either thinks they can get another job fairly easily or who feels that they can't be fired.