This part gripes me when they travel to “less fortunate” or “poor” countries where eating out is $0.50-2.00 but the same or similar thing is $30-500 in the US, however: people earn different levels of income. Like in that “third world” country, people may only live with $10 a day while Americans live with either $7.25 / $15 per hour in minimum wage, so it’s not comparable as to why the prices are seen as “cheap” by Americans.
Now, put it this way: if an average joe were to earn the FEDERAL mandated minimum wage of $7.25, is buying a whole weeks worth of groceries affordable with that alone (excluding rent, utilities, insurance, etc)? Do you consider a $200 semi-fancy dinner at a restaurant (not over the top luxurious, but formal & fine dining) with family or friends “cheap” in the US whilst earning $15 (or even $30) per hour in minimum wage?
You seem to be mixing two topics. One appears to be a complaint about purchasing power between tourists and locals, and the other about US domestic purchasing power on minimum wage.
You’ve got lots of great answers by others on the latter and how it is unsustainable as a living wage. Why Americans (and likely other Western tourists in general) consider certain countries “cheaper” is because of exchange rates. That would be a whole post on it’s own.
A single US Dollar (USD) can be used to buy about 93 Indian Rupees (INR), as an example. The average monthly wage is something like 25,000 INR, so even minimum US federal wage would be 5x more monthly buying power (but as explained by others, minimum wage earners are not the ones traveling). “Cheap” is used to compare against a similar purchase in their home country and what it would have cost there. It is not an insult but a way to describe the difference in cost relative to income.