Well let me put it this way, you're already at least £10m over what the last person paid for it at the most generous interpretation of that deal. We're worth whatever someone is willing to pay, and at the moment, it's apparently short of Donald's valuation. The squad may be worth £13m in transfer fees theoretically, but all of those players actually cost that amount each year. They're not just 'not worth £13m', they're a liability as much as they're an asset.
The club's most tangible assets are the stadium and the academy of light. Those are not quantifiable beyond the price of the land they sit on, such is their quite niche use at the moment, and the cost to convert them for any other purpose.