We had a call with them this week. Basically you pay a flat fee for a pool of traffic / resources. No longer billed by instances.
Most everything is now part of a single product: New Relic One. You pay for data ingest beyond the first 100GB and you pay per seat for seats after the first. The AI pieces have some additional costs after a certain point as well, but from my understanding the free tier is very generous.
source: Worked at NR 5yrs ago for several years on an agent team (frequently lamented pricing structure), joined again about a month ago.