My IDDP class has people from 17 different countries, really rich countries, diversity and mutual respect is basically common sense.
From approximately $250k (actual investment of a 2-3 year program for FTD) to $500k (your imaginary number) is quite a big difference just to start with, and in the long run is a very small investment.
Opportunities are endless, and using basic side-by-side comparison it is really easy to see that even though you could have a relatively good life as a dentist in your home country (or not), it is still worth a try investing time and money and becoming a licensed dentist in the US. Dentistry is on the top 5 of rising profession in the US, and 2 dental specialties are in the top 10 of the most well paid jobs.
Since I got here 3 years ago I've met and had the chance to interact and got to know the story of lots of dental professionals, international dental students, dental students, recent graduates from both international and regular dds programs, also professionals already established for quite a while, and I can't recall none of them talking about struggling to pay back loans or to find jobs. There's still a high demand for qualified dental professionals, like us, internationally trained dentists!
And if you think that the money invested on becoming a dentist is a lot of money, you might not have the slightest idea of how much money a dentist make... I can tell you that a dentist in my country that makes $100k/year is an extremely successful one, and I know that just by looking at simple stats and numbers that making 10x that amount of money/year is highly likely in the US.
Good luck to all of those applying for International Dentists Programs, if you all still have any doubts, just take a look around, talk to people, and don't discouraged by anyone, anywhere, anytime!
"The problem with the world is that the intelligent people are full of doubts, while the stupid ones are full of confidence." Charles Bukowski