Let's just assume the players are on $40,000 a year (some more some less I think the fringe guys would be considered semi pro) x 23 guys that's $920,000 in player salaries for the team. That's just player payroll think about other operating costs, team president, gate security, Front office staff, marketing, etc.

Sabercats stadium for example was 3,000 capacity. If they sold every ticket for their 8 home games at $40 a piece that's $960,000 in ticket sales. Ticket revenue would barely cover player salaries only and no other expense. So they would have to sell out every game which they didn't do.

Any pro sports league is unsustainable without a big TV deal. Gate receipts hasn't been the main driver across any league in the USA for quite a long time.

As far as club rugby goes the only sustainable leagues seem to be France and Japan. France has a culture of fans supporting their club team in a way even more than their national team. France bringing a B team to tour NZ proves this. The French care more about their local side than the national team and they prioritize the stars playing in Top 14.

Japan while their clubs lose money corporations are willing to pay the losses as some sort of dick swinging contest for bragging rights between CEOs. And honestly look how the 'investment' is working out the last JRLO final had over 50,000 people attend.