cold feet is cause by a few reasons. boots too tight or too lose. wet boots, or poor circulation.
some things to try are what people have suggested, unbuckle your boots if they are too tight. or if your boots are too big then they can get cold too, might need new boots, but if you have custom footbeds, that probably is not the reason. now are your footbeds custom or the ones you buy an d just stick in. if they are the kind you just buy, try getting custom ones and tell them you have cold toes, they will try to make the flow of your boot promite good circulation, at least they should try.
if you have poor circulation, go to your doctor and see if they have any suggestions.
try this...when you are done skiing, take out the liners and htent eh hard plasitc thing on the bottom, i guarentee you there is moistour int her that you didnt know was there. this is caused but melintg snow nad build up of sweat...if you dont let it air out it is in there and you dont know it and then freezes when you are skiing and makes your toes cold.
if all else fails i live by hotronics, i cannot ski without them becuase i have really bad circulation in my feet. i wear them, my toes will be warm but still numb thats how bad my feet are. but i love them! and if you cuz live.com and search them you and earn cash back and you cna find them on ebay for about 170 new. they are really easy ti intsall too.
good luck! cold toes suck!