It depends on if they still have the notability requirement; if they just charge $20 and anyone can get it then it definitely devalues the whole thing (the whole value of the mark other than as a signal is access to DM other notable people; if anyone can pay $20 to DM celebrities and stuff celebrities will turn off blue check mark DMs or if there is no option just ignore DMs entirely, which then kills the journalism loop on Twitter where journalists get access to celebrities, politicians, etc. by having the mark).