30$/user/year seems to be accurate. Facebook reported 86 billion USD for 2020 [1] and 2.89 billion MAU [2]. When computing the ratio, the geek inside me feels particularly satisfied to reduce billion from the numerator and denominator. :)
So 2€/user/month seems priced well.
[1] https://investor.fb.com/investor-news/press-release-details/... [2] https://www.statista.com/statistics/346167/facebook-global-d...