There are 2 museums at Coventry.
Airbase -
AIRBASE - The live air museum is the one on the airfield and will cost you £10 for entry. Interesting collection though I agree the entry price is a bit steep and the majority of the aircraft are hands off,
An easy walk off the airfield is the better value Midland Air Museum -
MIDLAND AIR MUSEUM which will cost you £5.00 entry. Good collection of aircraft and if enough volunteers are on duty you can scramble up into the Vulcan and play with the controls in the
Whistling Wheelbarrow.
If I had to choose one it would be the Midland which has a pleasant amateurish feel about it and a better display of aircraft, IMHO.