I think Busy is just willing to pay this out of pocket, because it hasn't been a large expense. They're treating it like a loss-leading promotion to get new users. In the long term, you are right that the costs for providing this could prove to be hefty and perhaps they will need to tone it down.
The ethics of busy seem to be solid.
I remain on the fence. For me it's a red flag that they don't mention Steem in describing what it is they're doing, always has been since day 1.