That's an 'how long is a piece of string' question.
We go into it for love, not money and certainly where I am, it's never going to make anyone rich. I teach a few classes a week because I enjoy it and love seeing the benefit it brings to people. Those who have traditional training will probably be versed in Yoga's 8 limbs which include moral principles like not being greedy/avaricious.
Once I factor in prep, insurance costs, marketing etc, my hourly take-home isn't much above NMW. But I only teach a few classes a week with occasional workshops.
Those who become teacher-trainers and run retreats can earn more and I guess someone in a wealthier area who runs a studio could do well.
There's also been a growth in yoga teacher business mentors - no idea how lucrative that is