Are we given a "wad of cash", or do we sell the broadcast rights to our competition in exchange for it like every other elite competition in sport tries to?

It's not something for nothing. Its a revenue stream just like any other. Get over it.

Unless you think that an average of only about 400 fans from each club would come on the day their team plays and no neutrals/weekend stayers are included, then you couldn't fit it in a 3k stadium.

I'd say 400 was a tad optimistic , and SL fans tend to care little about watching lower tier RL unless its free on the TV , so 3,000 would be ample

We watch all the games and absolutely love it! Been to all except the Scotland one (too far).

Been to what ? , this is about a potential Championship event , not SL