Absolute numbers. I saved at least 4 times as much in NYC. Don't take this to mean much since I am one data point.

Typically these are measured in absolute numbers. I'm not sure why you'd want to measure as relative ratios.

The ratio of savings:spending lets me know when I can retire early.

Using exaggerated figures, if I earn 100k in the US, save 10k a year but I spend 90k, then it's going to take me longer to retire than if I earn 35k in Europe, spend 30k and save 5k. Because in the US, it'll take 9 years to save enough to live off one year, while in Europe it'll take six years to do the same.

Of course you can move to a cheaper country when you retire, but you'll have to rebuild your friendships, adjust to the culture, etc.

You are taking the exactly correct way to think about savings: asset-liability matching, and being realistic about it (not imagining you can move to a new place because 'retired', so do, but many can not do so successfully).

But many can, and do. To each their own.

Indeed. But shouldn't assume the can, because that kind of assumption something many cannot survive.

Sensible planning is asset-liability matching.

But the win in that game is to save 10k per year in the US, then retire in Europe. Get full retirement in half the time.

Many do that within the US with cost of living games. Work in SF for 5 years saving 200k a year. Move to Flordia and be set living in 40k a year for life. (Or some variation thereof)

That works for some. But there is a loss of social capital and cultural capital in moving. Over a few years it's possible to build a new friendship circle (although I'm told that gets harder as one gets older). Additionally, while a basket of goods might be cheaper in Florida, as Rumsfeld said, there are unknown unknowns.

Perhaps Florida is more expensive than you might think because the cost of air-conditioning is expensive. And while lots can go without it, as a non-native, you might find the heat unbearable. I'm using this as an example of why it's difficult to estimate the true costs of living somewhere until you've put down roots there.

Furthermore, when you're on 100k a year and saving $10k, spending $400 on a new phone is a negligible expense. If you're on $30k, and saving $6k it is a bigger proportion of your savings. If you plan on moving, you're going to readjust your standard of living and your creature comforts.

Obviously your strategy can and does work, but counting on a move working out and being able to reduce living costs is a riskier strategy (with a potentially bigger payout), and it comes with its own costs.

Because i need to be able to cover the costs (i.e. what is the savings in terms of purchasing power rather than absolute savings). If i lose my job tomorrow and my rent is 2800, I don't really care that i save 1k compared to 700 per month (under the assumption i can't increase the purchasing power of my savings somehow).

One idea is that by investing a larger amount of money while living in an expensive area, later moving to a less expensive area (perhaps upon retirement, etc) will leave you with more assets to work with than if you had stayed working in the less expensive area the whole time (and investing a great deal less due to lower wages).