[thepasswordis]

He's saying:

"You are claiming that my app is costing you $20M a year in API calls. Just buy it from me for $10M. Then it's yours to shut down if you want, or modify, or whatever you want to do with it."

That's not a threat. At that point it seems like he didn't have any obligation to do anything, and was offering them a mutually beneficial deal. Reddit's cost go down by $20M a year, he gets paid, and everybody (except probably the apollo users) benefits.