I was just thinking about this today!

Here's my stats, although they're still subject to change based on tomorrow's game:

Income
Investment: 71.5%
Ticket sales: 0.71%
Sponsorship: 18.9%
Competition prizes: 7.94%
Transfers out: 0.91%
Merchandise: 0.03%

Expenses
Player wages: 3.53%
Transfers in: 82.36%
Win bonuses: 7.04%
Construction: 7.07%

Net profit: 8.21%


I think it will be a great idea to track these figures after every season and see how they change. These figures apply to a level 1 League winning team with no cup run.