I hope you don't take it as a harsh comment but I guess the charity event guitars were almost everytime guitars with no history, just taken for the event while the three mentioned auctioned guitars were the "real deal" where he played on in private, at BG and on tour. I often had a somewhat disgusted feeling when he donated a random guitar for charity, just as if he had found a good opportunity to get rid of it.
LE
Don’t quite follow the logic here. I imagine what would happen is MK would be asked to do something for charity, he would phone up Fender and they would provide a guitar, either at cost price or maybe free as part of their own charitable efforts (probably some sort of tax write off).
Charity makes money, winning bidder gets something nice, MK looks good, everyone wins, no need for disgust.
As for insurance value, people got swept up in auction fever at the guitar sale. I doubt anyone is paying £126k for an MK Strat anytime soon.