we supposedly get 11,500 tickets for the final. Even taking off 10% for sponsors, players etc that leaves over 10k for fans.
I suspect every fan who has an account (ST, gold and members) will get one.
Flights are not cheap (now) and a mid week game may put off a fair number of supporters due to age, kid responsibilities, work commitments etc.
In Krakow i reckon there were 4k Palace in total and it was pretty easy to buy in the home/neutral end so even doubling that and that still leaves some slack.
I wouldn't panic.