The original estimates were simply for building a space station. The new, much higher estimates are for building it and operating it for many years. No estimated operations costs were provided in those earlier numbers so you have an apples and oranges comparison.

While we're on the subject of higher than projected costs (as well as apples and oranges), why limit it to the space program? Why not scrutinize other governmental programs such as Medicare. When Medicare was established in the mid 1960s, its projected costs for 1990 were $9 billion. The actual costs were over $100 billion - an overrun of more than 1000%. It's now running over $300 billion a year with no end in sight.

How about other things, like quite a few military weapons systems or something as seemingly straight-forward as Boston's "Big Dig", which is years late and several hundred percent over budget?

Perhaps the one common theme here is that government programs very often end up costing far more than projected, regardless of whether you're talking about military, social, or space funding. There's far less accountability in the government to overruns than in the private sector. The government's attitude seems to be, so what if the program costs several times the forecast? We can always take more tax money from the people to pay for it, regardless of what it may be.