As seen in places like Los Angeles and New York, the more popular an area is, the more expensive items become. Sellers in developing countries are generally able to sell their items at significantly higher prices, thanks to the general tourist mindset that they are supporting the local economy. Although they are, sometimes this will mean that these jobs make more money than socially crucial jobs, such as doctors or teachers. This causes a lack of professionals to provide for the locals, an inflation of money so that not much is affordable, and as a result - impoverishment, collapse. It becomes detrimental and only helpful to a few and not all.
This may not be the case for all countries. This argument does not take into consideration the nature of people. Sure, some may be greedy and take the job that provides more, but there will always be those who want to be selfless and provide. People are not inherently focused on just themselves.
[P1] Sellers increase prices to make more money. [P2] Prices become too high and people are less likely to enter socially important professions.
Rejecting the premises
[Rejecting P2] This will not necessarily make people not want to enter socially important professions.