They aren't reliant on RFU money though afaik - it won't kill them. If it was that easy they would have done it by now.
Their BT deal is a reduction in monies from Sky if there is no Euro competition.
They do receive quite a few million (distributed) from the RFU.
The PRL herd is only as strong as their weakest buffalo.
I definitely think, if the RFU wanted to, they could take the RFU championship - subsidise it, put it head-to-head with the PRL (who would be standalone with no relegation and no-one to replace busted clubs) and win.
For example, if the RFU can get Wasps' back to the wall the PRL are in trouble [i.e. go bust or accept our buy-out and move from PRL to RFU championship] the PRL league drops to 11. Put Sarries to the wall and the PRL are screwed. Neither are in a good financial position right now.