The bed-bound 60 year old's expensive needs would presumably be covered by the universal health insurance. His non-health-related costs would actually probably be lower than a 20 year old's, since he of course doesn't do anything and probably doesn't eat as much.

That would work well if all of the support needed by the disabled person fell under a single universal healthcare program, but it often doesn't. Disabled people often need non-medical assistance as well. Those are often separate social programs.