Define “mass tourism”. If we’re simply going by tourists per capita, or better tourist-days per capita, there’s plenty of places with very high numbers that are doing well – but those aren’t cities, much less vibrant ones. They’re things like mountain villages with ski resorts, with a couple of original farms offering a couple of rooms, a few smaller hotels dotted throughout, plenty of seasonal workers and when the season is over the whole villages resumes to what it has done for millennia: Subsistence agriculture. Maybe some forestry, and there’s also a sawmill. At a way higher living standards than would be possible by exporting cheese or whatnot.

…not speaking about extreme places like Davos, though, nothing is normal or typical about that place. They’re also more than rich enough to afford public housing and democratic enough to actually build it, YMMV in otherwise comparable places.

What basically never works out economics-wise is all-inclusive resorts: Those are generally built by outside investors, capitals thus flowing out of the local area, they may pay the local residents well in season but out of season they’re out of work and local non-tourist industry has to deal with not being able to afford workers in season. Some may be able to adapt but you can’t just shut down most factories, physically and/or because you need that operation time to pay back your loans. Thus the local industry gets killed off, or can’t develop in the first place. Not going to happen in that mountain village because it never had the chance to develop anything serious in the first place, geography and all.

Oh, other example: Wacken. Just over 2000 inhabitants, maybe 6k taking surrounding municipalities into account, each year visited by 80-100k pilgrims. About 10% of the inhabitants flee during the festival, the rest is hustling. It’s short enough to not disturb the local economy yet brings in tons of money.