> The largest cost by far would not be bandwidth or storage but rather the cost to index these relays. By several orders of magnitude.

Touché, but I was talking on an individual relay scale, not global scale, to be fair.

That's a bridge that we will cross once we get to it.

If the majority of nostr clients will stick to being this global x-like (kind 1) feed, then yeah, you are absolutely correct, that's something that needs to be solved, but I forsee nostr eventually evolving to something else.