Although cost overruns are common in any large construction project, those over runs even if multiple million $, would be relatively minor in comparison to the Brooklyn property selloff. One Billion is one thousand million. Recent estimations I've seen are well in excess of $1B from the Brooklyn selloff alone, some estimating closer to $2B.
Perhaps those funds are considered as investment or capital and will not be used for day-to-day operating expenses.
I suspect the contamination was identified before the Warwick and UK properties were even considered and therefore, WT was able to purchase at a highly reduced prices, with the expectation that 'slave' labor would be mainly used for cleanup. Consider how many JWs would take a leave from work to travel across the country at their own expense for the 'priveledge' of helping at Bethel.
Although most of us think it dumb to purchase contaminated property or they didn't realize the contamination until too late, I think they knew full well and took advantage of any government assistance they could obtain or action against the prior owners, to offset the expense of restoring the properties.
It seems when you say the new Bible costs a fortune to produce, I expect you are thinking in terms of normal costs for a For Profit company which must pay salaries, vacation, benefits, insurance, income tax, property tax, paper, ink, and other overhead costs, in addition to making a profit.
Although there would be time required for translation, again, slave labor. Since there would be a limited number of word changes from the previous NWT, a computer could quickly identify those changes, likely from a digital English master document, so that the translation 'staff' for each language, are only required to concentrate on the changed text so that syntax is appropriate.
Regardless of WT's current financial situation, perhaps those at the top have realized the decline in first world JW membership and are using this opportunity to accumulate as much money as possible before the current money pot dries-up.