Just to let you aware, I have come across an exploit that should be patched. I verified this by multiple buildings and elevator shafts. When you buy "whatever" you select it brings up where you want to build. The trick is to have just enough for what you're buying and then spend all your money breaking rocks. When finished, place your building and it takes your remaining cash which is under 125 caps. Anyone else please reply to this thread to verify results.

For example I buy a 600 cap building, and then break 600 worth of caps in rocks. Left with maybe 13 or something small I then place my 600 cap building for the 13 or something caps and it works. I laughed.