Level 11 - 73,000 stadium $15 tickets attendance 73,000 fans
Level 12 - 91,000 stadium, $15 tickets attendance 91,000 fans
Level 13 - 111,000 stadium $20 tickets attendance 111,000 fans
Level 14 - 133,000 stadium $20 tickets attendance 133,000 fans

Not exactly a attendance cap but a good guide for what attendances I got in my club.