AAA Michigan is selling PKI tickets good any day of the 2004 season for $20 (all ages) if you buy by June 15. If you are a AAA/MI member, you can get them here. If you are a member of another AAA chapter, you *might* be able to buy them via the AAA/MI web site, or you could try calling a MI branch.
Chances are good that other area AAA chapters have the same deal. FYI.