I think you spectacularly missed the point that Mammabear was making there.
Of course no healthy and able-bodied person genuinely envies the serious life-limiting medical conditions and disabilities that many of us have; but they quite happily envy us for the money that is spent by the state to attempt to slightly mitigate the permanent everyday challenges that we go through because of them. Funny that, isn't it?
If the government offered to give everybody with a serious medical condition a free holiday to the seaside or unlimited Costa vouchers, I would completely agree with you; but these aren't pleasant things to have - they're essential lifesavers, many of which also come with unpleasant side-effects into the bargain.
They're all things that replace what you and most other people are privileged enough to already have. Properly working body parts are much, much, much better than needing to take drugs every day as a shadow of a replacement for their function when they don't work properly or at all.
This is the thin end of the wedge. If we're going to make higher earners pay for prescriptions, why not GP appointments? And if they ever need an ambulance and/or treatment in hospital, they can pay that themselves too instead of getting it on the NHS?
Why not make people who are high earners and also privileged enough to have no health problems beyond the occasional cold to pay an extra 'gratitude' tax, based on all of the money that they get to keep for themselves because they don't need to pay for loads of prescriptions for any serious lifelong condition that they're lucky enough not to have? Would that be fairer all around? Or would it be as ludicrous as begrudging people lifesaving drugs and treatments for ongoing serious illnesses?
Honestly, I think some people would gladly stand next to the wheelchair ramps to public buildings, angrily charging a toll to people daring to use it whom they believed 'could afford to pay it' - all the while paying no attention whatsoever to all of the able-bodied people freely using the stairs to get in.