@bu11durm personal opinion only; I can't back this up from the IRS website.
You bought all the tickets at the same time.
presumably there is a 'face value' printed on the ticket. That is part of your accounting refcords.
That is your cost basis; if you were given a discount for buying all 40 tickets at once the same discount is applied to each and every ticket.
the fact that the market value of some tickets increased (the team later increased the price for the better games) has no bearing on your cost basis.
