All of those sources are discussing average outcomes across the entire population.

None discuss outcomes among only those who "have the means to afford it" so none of them refute GP's claim.

Correct, where do the princes and sheiks of the Middle East head when they need the best medical care money can buy?

I’m not at all convinced they look carefully at health outcome and cost efficiency metrics before deciding where to point their private jets. Instead, I’ll bet (in part) they use high cost as a surrogate for quality. And the immediate availability of any test or consultation they desire.

A big part of why we spend more is cultural and environmental. The government incentives encourage unhealthy food to be everywhere and subsidizes things like adding corn syrup products to everything. Policy also encourages driving instead of walking. And we've made it culturally acceptable to be fat. There are big movements trying to convince people their weight is not a problem, not something they have control over, and you can be "healthy at any size". Many doctors have stopped warning patients about their obesity because of social pressure not to fat shame! I started with a doctor like that when facing blood pressure and related issues and have since ditched them. Caring more about sensitivity, being accused of fat shaming, and expediency than my health is malpractice in my book.