You suggest that when you go to another currency region you're ready to spend without giving much thought to the actual amounts you're pulling out of your pocke

You suggest that when you go to another currency region you're ready to spend without giving much thought to the actual amounts you're pulling out of your pockets? Because if you do care about costs you're presented with, there is no way around the aforementioned "mental arithmetics" (due to the exchange rate, of course).