Insurance in tournaments

[Lohu79]

I´m sure everybody has seen (or at least heard about) phil ivey recently giving insurance to phil helmut at a wsop final table not once but several times.
I haven´t done the proper calculations yet (nor collected the data) but i´m certain that helmuth gave away thousands of dollars ev-wise. He (seemingly) didn´t know the proper odds for the all-in matchups, thereby giving ivey the opportunity to hustle a bit, and of course ivey collected a little fee for giving insurance. But what´s more important: Tournament chips aren´t really worth their nominal value.

My question is: Did anyone take insurance in a tournament himself, and for what reasons? How much did you pay for decreasing your variance?
Furthermore: What would be the proper way to calculate the real worth of a hand being all-in heads-up in a tournament situation?