So for use cases where you need the user's consent because you don't have a different GDPR-valid reason for processing data (many reasonable use cases don't need consent, but user tracking for advertising generally does), that processing is permitted only if that consent is freely given i.e. willingly 'gifted'.
One way how it's implemented is that if some service if conditional upon 'consent' then there is literally no way to get 'GDPR-valid' consent - the user clicking 'I consent' to bypass a paywall doesn't count as the user consenting, and neither does signing a personalized pen&paper contract saying that the user consents to tracking in return for getting free use of some service, because that's not "freely given consent" and so it doesn't permit Meta to track that user. It's just like signing a contract where you get $10000 in return for agreeing to be enslaved for some time - your freedom is not something that can legally be sold, and so are the privacy rights.
The other way how it's implemented in GDPR is that it must be possible to withdraw consent at any time (including 5 seconds after signing up to a service) without any adverse consequences such as the service being cancelled or increasing in price. Obviously that's not a problem if the consent is freely given, but if someone tries to figure out some roundabout way of buying or trading for consent, the consequence-free cancellation makes the point that it's not supposed to work that way.
Of course, companies are not required to provide any service, and they can require a fee for some services - however what they can't do is buy 'consent' with discounts or free service; the GDPR limitations to tracking users are intended to apply to all tiers of users, no matter what Meta does or wants to do. Meta can gift users free service; users can 'gift' Meta consent to tracking, but they can't make a binding contract on that because under GDPR conditional consent is literally meaningless and worthless.