I'm going to leave it here because I'm obviously missing something. If, as you say, we pay into the welfare system with the highly unlikely event of benefiting from it, why not eliminate the cap, stabilize the system and have the high earners receive their standard benefit at retirement time?
FWIW, I'm quite far from a "soak the rich" mentality having posted here many times on the shortsightedness of that approach. (And being among the rich myself). But to me, this is more like the current graduated income tax, where high earners are taxed more yet receive no greater benefit. If the system is so much at risk that everybody is going to be hurt, it seems to me that removing the cap is a logical option.
The rich would pay more, as usual, with everybody benefiting. IMO, whatever calculations are currently in use are not necessarily sacrosanct.