Agreement with crosscourt, and in fact there are a couple other reasons also:
It's actually carried below cost now, due to depreciation, so the value on the books is negligible.
They haven't had appraisals yet, so even if they wanted to carry it at maket value, they don't know the market value. Until recently it wasn't worth this much. It was worth a lot because of the growth of Shenzhen, but then the creation of this special economic zone and the rezoning of the land multiplied the value last year. Among other benefits to this land, qualifying companies can get 15% tax rate instead of the usual 25%. That alone is obviously a huge deal, nevermind being in a massively populated area, right next to Hong Kong, 6 miles from Shenzhen's airport, and sitting on a highway.