He wasn't literally offering to sell out for $10 million. What he was saying was that if Reddit was being honest with the claim that Apollo was costing them $20 million per year in server costs, the obvious business decision would be to offer to buy him out first, thus bringing in those users with much less friction.

The fact that they're instead choosing to be manipulative (unrealistically short period for apps to adapt, API prices far above what other services charge) indicates that the $20 million number is a lie made to make themselves seem less scummy.

As it stands, Reddit hasn't even tried even simpler solutions like returning ads in the API requests and requiring that the 3rd parties include those for free usage.