I guess we will see cannibalisation of income from relays where there is too much overlap, but I don't see this as a bad thing, I see that as a sign that this market is serviced and you move on to the underserviced market, the smaller relays will always be chasing the niche interests

Bigger HPR (High-performance Relays) will compete with larger categories, if we only take social media IE Twitter/Reddit style posting, I think there's a place for everyone, small relays would be servicing more obscure categories like collecting antiques or some random thing, (we still have so many of these forums up today)

Then HPRs could focus on broader categories of appeal like Gaming, Movies, Books, stuff where a lot of people overlap, have an interest, and create content

I think client HPRs would source from other HPRs and smaller relays looking for content that gets the most engagement, and feed it up to their relay and client, because their incentive isn't to house content but to serve content that brings in the most users and increases time on site

As for payment, I think yes some HPRs would take up a bunch of the subs fees, but I wonder couldn't they request indexing from other relays for popular content and then pay them for doing that discovery, so the ones getting the most income from subs still feed relays who do the work sourcing content