But the only decision on the table was to go now, or not to go now. There is no requirement that he goes to London at all (though he probably will.) So I think he applied the concept of sunk cost perfectly. And more importantly, it would be a hard thing for most people (my wife especially) to do, that being ignoring the sunk cost. Me, I'm pretty good at putting decisions already made where they belong, in the past.

There are also costs he didn't include. If he went to London he would have the additional costs related to travel; hotels, food, travel within England and so on. Those also have to be factored into the equation. Does he go and get the benefit of the sunk cost while incurring new costs, or does he stay home and not get the benefit of the cost. When discussing sunk cost, in terms of getting the value of it, should additional expenses be considered?

Nancy