For those who do the calculations every year and change 'suppliers' - how long does it take you (in hours) to trawl through all the sites and make your decision? And how much are you saving in a year? So how much are you earning for each hour's work. That will tell you whether it was worth it - and I would be interested to know.
Of course, if you enjoy doing it then it's worth it anyway, but I would HATE it.