Do you trust Indian Developers? They can offer a lower price to dev your app. For ex in France it’s around 40-50k€ for a social network app, and in India it’s around 10-15k€. What’s your experience?

I've had both good and bad experiences, but that's everywhere, not just India.

Trust but verify. You need to be on top of them to get a good outcome. Delays are common, revisions are plentiful. You can get good work out of them if you're willing to put in the time and effort.

Indians are going to non-scalable code. You thing will break in a week (even if the frontend sounds satisfying to you). Unless it's an Indian born and raised in US, I would say you're better off spending your money learning how to code yourself.

I think it's a mistake to group all Indian developers in the same pot. Yes they're cheaper but you're still going to get a mix of good and bad programmers. If you're not sure how to tell hire a consultant and talk to a bunch of Indian programmers about your needs and their skills. Just like everywhere else, don't take people on face value... ask for code samples, previous work, etc.

You get what you pay for.