It’s impossible to know whether the same dollars Ford gave to EAA were later paid to the band. I assume sponsorships go into the same checking account where admissions, camping fees, exhibitor fees, etc., are deposited and out of which various AirVenture expenses are paid.
Unless you happen to know, just because someone is credited as a “sponsor” does not mean they paid the entire cost. Even if so, it doesn’t mean EAA couldn’t have gotten Ford to sponsor something else instead of the concert. So at least it cost EAA the opportunity to get something else sponsored.