I'm not sure you guys completely got what July Forth meant, especially by saying "spot on" ... or at least I assume he did, as one of the senior managers around.

Yes, 2500 is probably the "attendance cap" for level 2, but that's not the right term to use. I'm not sure if you could possibly have more than 2500 fans on level 2, so that's a possible reason why no more than that would show up in this case, but that would be due to the simple maths of how many fans can you attract per match/trophy until that point.
There isn't a cap of actual attendance, there's a limit on how many fans can give you possession bonus, so that you don't get more than 5% per match. Lowering the ticket prices WILL give you higher attendance, but if 2500 already give you 5%, then for a 3000 seat stadium it doesn't make sense to lower it as you'd get lower revenues:

- $4 tickets: 4*2500 = $10000
- $3 tickets: 3*3000 = $9000

That's for the "attendance cap", but there's another thing - @festinator was spot on on BOTH suggestions. The team that you play against does make a difference AND so does the competition.