Well fair enough, curious about the expense part though, wouldn't it be a fraction of the cost of other relays? Because you're only serving up a filtered selection? Is the cost for the compute?
As for clients, I had always just created a custom feed with just that relay, which is super-easy in #coracle . My understanding is that #jumble is exclusively relay-based browsing (which I never really got, but lots of people seem to think is the "right" way to Nostr)...