I think it accurately reflects the market value of the club. Nothing sinister, the club has become a money pit with minimal asset value and overheads way above income.
On season tickets alone, I'd be surprised if the average is as you say. I'd go for 400 at the very most. Given the vast majority buy at early bird prices. ( and given multiple concessions, oap's, u21s and kids at £29 )then there is vat to take into account. At 20%. £2.5m would be nearer. I'd have thought. It's a reason why Sponsorship and other income revenues make up the majority of funding.
Often the case where the club and stadium are split ownership wise. Which is why it’s always a negative situation. Yes it offers protection, but it doesn’t help the club.
I was surprised the club accepted such a short lease tbh. (Unless there's a reason why it can't be longer ?) I'd guess a hundred year lease may attract more interest if they were considering putting it on the market in the future. (However long)