This is a lucrative although unethical income for much of the world. I'm an Indian dev with 10 years experience in relatively cutting edge tech and 3 interviews would match my salary.

That's why you use the homework as a final step, after screening CVs, technical interview etc. Taking a burn from time to time from a candidate not really looking for a job yet willing to go through hoops is surely more reasonable for a company than burning all your candidates by the equivalent amount, no?