Re: How many Shuttles could have been kept operative..
""The Wall" might cost as much as 30 billion"
The US-Mexico border is around 2000 miles. $30 billion works out at $15m / mile.
The US government's own budget office estimates that the cost would be $24m/mile for the cheapest possible option, which is more fence than wall. Average US government projects overrun budgeted cost by a factor of 3.3 ON AVERAGE. So it's probable that the fence would cost almost $100b, and a proper wall at least half as much again, probably double.
(https://www.cato.org/blog/cost-border-wall-keeps-climbing-its-becoming-less-wall)
Biting the hand that feeds IT
