While I believe the terms and conditions of the POA classifieds require an asking price, it really is irrelevant in this case. He might as well list it at $1b. Hangar transaction prices vary based on the structure, location, length of term, airport development plans, the market, etc., so information collection on the asking price of ground lease a lease at one airport has no bearing on the selling price of a hangar at any other location...or for that matter, even that airport. The price will ultimately be determined by negotiation.
I'll further add, what a seller's indication of the airport management's intent on extending the lease is irrelevant. Short of a renegotiated lease in hand, you have to assume the property will revert to the airport sponsor at the time of termination. Reviewing the airport's approved ALP (airport layout plan), or looking at the lease terms of adjacent structures may give you some onsite, but airport commissions change, managers change, and ALP's change. There's no guarantees.