Not base pay, but OKTAGON and ACA have run $1,000,000 grand prix/tournaments.
Several fighters have said they make more competing in Europe than they would in the UFC, but they don’t mention specific amounts
A friend of mine got an offer from ACA for $2,000 / $2,000, but that was an offer he received years ago and he is experienced, but somewhat unknown so we know they weren’t going to break the bank for them.