AFAIK there's no formal mechanism for bidding on naming rights, but Twitter could easily set up an auction platform, take a small cut off the top, and do quite nicely.
They may not do anything about it, though, if @substack is being used. Logging into Twitter is enough to keep the account active. I don't know if that is changing with the new owner. I know that Musk said they will be making names for inactive accounts available soon.
Or, to take a page from 'Radical Markets', twitter accounts could be associated with a reservation price (a price at which a person would definitely sell), and 'taxed' (re: charged) a proportion of that reservation price. I believe it was Patio11 who observed that his upper limit on willingness to pay for twitter would be very high. Right now, Twitter doesn't capture any of that.
That might only work for bluecheck accounts, not sure. I don't want to lose my random 10 follower account for $100, but neither do I want to pay to be a lurker