I dont think it was wise to purchase Teesside for £40,000,000 when Peel purchased it for £500,000 just 16 years before, but the mayor clearly had an elected mandate to do so.
The real question has to be asked was why the 6 local councils sold their share for 500k to be split between the 6 councils. When the land value was about £40m back then, the councils could have at least sold their shares for many millions.
So in reality the mayor has only paid market value for the airport.