Been reading through this thread and realized some people pointed out that its not normal to get above 21k fans for a normal team.
I do know of a team which basically draws above 21k fans every game, even in cup matches against bots:
(107183)He has a 28k seat arena. But his highest attendance after his last price change just earned him $387k, which seems to be relatively low for a div I team. He's made the playoffs 7 seasons in a row but is currently lying 6th place in his conference with a 2-4 game record, so frankly speaking I think it might be possible to bump up your attendance to 25k maybe? The drawback might be lower revenue.
That said I just realized that I go with a similar ratio to the 15k bleacher 5k lower tier (I have 6k tho) as well. Can't remember how I came up with it tho.