814man, the charge is levied by the Tour Operator.
Not one penny of it goes to the airline that has the hassle of arranging for the handling and carrying of the darned things. The airline gets the money if you are charged excess baggage because the weight of the skis and boots takes you over the personal baggage allowance on your ticket.
I was told some time ago that the charge for carriage of skis was brought in by the tour operators when passengers started to take their own skis with them rather than hiring from outlets in resort with whom the tour operators had commission arrangements. This way they made up for potential loss of revenues.
Scheduled airlines are a totally different kettle of fish.