There are some huge numbers and huge discrepancies on this thread in relation to Temple Farm. I did a bit of research. Here is how I see the likely actual figures (in rough ballpark terms).
A description of what is being built at Chelmsford is here:
http://www.chelmsford.gov.uk/temple-farm
Note that it states 112,500 sqm of "mixed use development". That would probably be gross floor area, as I read somewhere that it is only 22 acres (around 90,000 sqm). "Mixed use development" is a reference to the project containing both residential and non-residential, as I understand it.
A brief review on the internet suggests it would cost at least £800, or more per sqm to build something like that. (Obviously, that is just a guestimate.) Perhaps with volunteer labor, that might come down to, say, £500 per sqm, but I doubt it.
800 x 112,500 = £90 million. That is just a ballpark figure. It could be way off. Also, that is only the cost to build. It does not include the original purchase cost, printing presses etc. It sounds as though there are some significant site contamination issues to resolve as well, which would be expensive to resolve.
£90 million is a big project for the UK branch to take on, if the following link to their financial statements is correct:
https://jwleaks.files.wordpress.com/2012/07/2014-wtbtsb-financial-report.pdf
That financial statement, compared to earlier ones (I haven't included) suggest that they have pulled together £50 million in cash, presumably for this project.
I don't believe the completed project would be saleable for anything like £3 billion, later. It is not like a house or a standard commercial building. Any future owner would have to modify it extensively to suit. The project may only be worth land value when complete. I don't know the area, and have never been there, but I tried to get a rough idea of land value in the area, using real estate websites. It seemed to me 22 (uncontaminated) acres in that area may be worth £20 to 50 million, but I could be way out.
This does not look like a real-estate play to me, as it would be too difficult to on-sell on completion. It seems like a project conceived in better times, but is now in difficulty. I note there is another thread where there is a rumor that only one part will be built.
By the way, I am not an expert on any of this. There must be others in a much better position to comment.