One thing that Factfulness does is take a more nuanced look at wealth. Rosling makes 4 categories of prosperity — the majority of which by population are in the middle, neither ultra-rich nor ultra-poor.

Something he wrote that helped me understand: From the point of view of the wealthiest societies, everyone else looks poor. But there's a huge difference — in quality of life — between subsistence-poor and bike-to-the-market poor. In the second category, your children are probably going to finish high school and have a chance at professional careers. In the first category you're one injury or bad harvest away from disaster.

That's true for penicillin, but what about more exotic medical procedures? "Socialized" medicine is railed against for "rationing" but all markets have rationing as well. The whole point of a market is to ration resources to those most willing and able to pay.

But yes. In general the line that matters is "Can I afford it?". If it doesn't exist, the answer is no for everbody. If it does exist, and has a price tag on it, the answer is no for some people and yes for others. The "no"s in the latter situation are pretty much in the same situation as they were before the good existed.