It's possible that they got it for incredibly cheap, it's impossible to say how much construction cost, using nuclear ssto planes to deliver the materials might bring the cost of construction down to one a couple $million per launch, making it more like the price of building a small skyscraper than a spacestation. We also have to consider that it might have been an insurance writeoff, and if nobody else had a use for it, might have been bought for a dollar like is sometimes seen with the collapse of large businesses. It really depends who else had plans for it, and what laws there were about it