Open sats putting in over $500k per month as of 1.5 years ago, surely that's a fair amount higher now? And then HRF, and then VCs like Ten31 and Hivemind, etc. And Jack's latest $10m for andotherstuff to last a year or two. Could be well over $1m per month right now, mostly going to developer salaries. Maybe $2+ million, who knows? Money coming back in the form of actual income (subscriptions, etc) is a negligible fraction of that.
If the developers stop getting this funding then they'll find other work and the protocol will atrophy, become much smaller with fewer projects maintained by die-hards in their spare time. Happens pretty much every time mass initial funding dries up without healthy recurring revenue streams to take the place. So it's a real gamble right now.