There's no incentives for Facebook to "sell" their user data as long as this is the primary advantage over their competitors including Google, Amazon, MS, etc. Big techs naturally tend to monopolize connections to its users and FB is no exception.

In fact, if they "sell" their user data, anti-trust regulators will be very happy; they want big techs to share user data to its competitors but the big techs are using user privacy and security as their excuses to rule out new competitions in the industry. Apple took the lead and other big techs are now following.