I think I get it – it’s a math thing.
Let’s say that there’s a 1/10 chance of a big player hitting a jackpot (100,000), 8/10 chance of being a small loser (10,000), and 1/10 chance of being a big loser (30,000). Yes these numbers are inaccurate, but they make the math easy.
You have ten big players and are on a 50% share (again, a math assumption) and everything goes according to probability.
All in one casino:
MGR of 10,000 (110,000 – the big winner) means you earn 5000.
In ten casinos.
One winner – MGR -100,000 = no payout.
Small losers – MGR 5000 each (40,000 total)
big loser – MGR 15,000
You earn 27,500.
Hope that makes the point clear.