Acutally, it has nothing to do with living into an old age, and everything to do with choosing to live abroad. It would be the same for me if I wanted to retire in the south of France. My Medicare wouldn't follow me.
My reference is to private medical care: insurance. That was what was costing € 3600 in the last year of keeping it. Age, of course, is the factor that usually kills off your earning ability, mine being photography dependent. I thought I had that one covered with stock, but it turned out to be a false sense of security. Age is also the time when nature makes you more dependent on medical care. I had two heart attacks on private medicine care after hitting 65, and my late wife several cancer ops.
Chosing to live abroad is not a sin, though there is the mindset that sees it as exactly that, and to make it worse, an escape from an environment many others, could they but, would gladly opt to make as well. Inevitably, this raises envy and associated hatreds.
Your Medicare is a separate issue: as far as I can tell, you were never in an international arrangement where such was possible; we were and, for the time being, still are. As you raised it first, I feel I must ask the question: given similar choices, would the South of France not perhaps have felt to be an attractive option, whether or not you chose actually to take it up?
That is a very important aspect of the entire mess: everyone in Britain, had they wanted to, had that opportunity for mobility and thousands enjoy its fruits every day. Now, that will probably be rescinded, and for what? For the satisfaction of a bunch of bigoted, self-serving and lying politicians seeking their place in the history books; you must understand that in Britain, every outgoing prime minister is saddled with media assessments of his/her legacy: it has become a parlour game. What is legacy? Apart from Churchill and, possibly, Thatcher, few latter day ones have actually made any real, positive mark on the national destiny.
Do you think Farage or Boris would turn their miserable backs on a place in that historical archive, even as lowly and negative a one as Guy Fawkes?
As for the financial benefits of leaving - there are none. Existing trade must inevitably suffer, jobs in manufacturing lost if only because of the system of parts being shipped to and fro across open borders in just-in-time manufacturing work flows. When borders reappear, customs controls re-established, checks made on everything (otherwise, what's the point of them?) that passes, it becomes counter-productive and expensive having factories spead across a continent. Anybody imagine the work will suddenly be concentrated within an external, and small part of the market? Unbelievably, there are guys in British car plants thinking exactly that. Well, they were, until recent Japanes decisions changed the landscape, but instead of accepting they were mistaken they now say hey, let them go! We will survive! Producing exactly what, may I ask?
It is impossible to get into any branch of this topic without being affected by the ramifications of each such on all of the rest.
Mega mess.