haha too true John, we've already had a serious cost overrun, I think twice the original budget should cover it... it's the little things that you don't factor in... everytime I go down to the engineering shop to buy a couple of bolts, it usually costs around $100 or so by the time you factor in the grade of bolts, the head type, washers, locktite, some shiny new tool that they have on special etc...
in future, when I budget, if I can itemise it, the minimum price I'll allow per item will be $100... I think we've spent a few hundred dollars on hose clamps alone... gahh, I don't want to think about it...