Many devs do. Do you really think he'd be putting all the time and "effort" if there was no money involved?
It's a choice for the people that support him. They're not held at gun point.
If they decide to financially support him, understanding that it's a hobby, that's their business, not yours.
Who are you to pass arbitrary judgement on how they spend their money?
No-one has been misled & they can stop paying any time they wish.
How you deduce they're "being milked" is beyond me.
Why that would be any concern of yours is also puzzling.