Consider that a subsistence economy is largely lacking in currency, so jobs that pay cash are certainly more attractive that working your own corn field. But I've talked to a lot of people that work at the mines. They aren't attached to their jobs, but they'll do it while it (or they) are still around.

You make $2 a day working in a farm. I'll pay you $3 a day to poison the river that irrigates the farm.

Is the job I'm offering you a net gain for your community? It's certainly a net gain to you, and me...