I think they book it at cost or if they get it for free, what it would have cost them.
This is what the 10-Q says
"Land use rights represent acquisition of land use right rights of agriculture land from farmers and are amortized on the straight-line basis over the respective lease periods. The lease period of agriculture land is in the range from 10 years to 60 years. Land use rights purchase prices were determined in accordance with the P.R.C Government’s minimum lease payments of agriculture land and mutually agreed between the company and the vendors. No independent professional appraiser performed a valuation of land use rights at the balance sheet dates."
It's as close as one can get to "fair value" IMO.
They have different types of land depending on its location. Agricultural land, Residential land, Industrial land. Also, the closer to urban areas the more expensive the land. The $265M (for 55%) for 3,000 mu in Zhongshan sounds right to me. $3 billion did not, LOL. It's a lot more expensive than the land they use for free at SJAP in the cold North.
It is then up to SIAF to turn it into a buck. No doubt the Mega Farm will do very well. LOL.