I read the upgrade info at allears.net and I'm wondering if I buy my MYW tix from another source, such as Ticketmania, and then decide to upgrade to APs, does does Disney use their cost for determining how much I pay for the upgrade or do I have to show what I paid for the tix? We are considering doing an upgrade, but not until we are at the parks. And we will probably buy 7-day hopper passes through Ticketmania. I'm curious to know if I need to be sure and bring my receipts for my tix. (Probably should do it anyway, though).
Has anyone done this before?
Thanks!