Generally speaking I've seen no shortage of reminders on Nostr that folks need to pay for what they derive value from but most of the advice on how to pay or what exactly you're paying for isn't always clear, especially for us normies.
Satellite.earth CDN has been one of the simplest to understand IMO, partly because the link is right there in the home page of the client.
Service providers, don't be afraid to ask, and don't be reluctant to explain.