I've heard that they count full madness as 3 tickets, but the numbers don't quite feel like they add up. If you say there are 40k at main stage (which I think is on the lower side of estimates) it means there are 26k on the other 15 stages, and/or walking around (the paths at nights are totally full). If each other smaller stage has an average capacity of 2k (again, I think this is low) then that's 30k. Plus the people walking around or eating (3k? 5k?) I'd guess the number would be around 75k at a conservative estimate. Possibly over 100k if you use 50k main and 3k other stage average.

I know they aren't your numbers so that's not an attack on your post - just me brainstorming out loud :).