Devs have been reluctant to set prices, so that they don't accidentally lock people out, who can't afford them.
That has led to the idea that everything should be completely free to use for everyone forever, but satoshis have 8 decimal places.
We should simply experiment with different pricing models.
nostr21.com costs 21 sats one-time and just offers spam protection and good management, nostr.wine costs a lot, but opens you up to their other premium services and the filter.