In the end, at least at the destination resorts, the elasticity of demand seems to be measured correctly since it seems that the market is paying these prices and lessons are booked solid over peak season. Would tips be higher or lower if private lesson prices were significantly dropped? I'm thinking tips would be lower as lower income people entered the market where currently just higher income people are paying. So, it's arguable that these $1,000/day plus price strategies yield higher tips for instructors than a $300/day model would... After all, it's not like you can work more than one all day lesson right??
I do hope people tip ski instructors if they had a good experience. Unfortunately, that does not seem to always be the case. As an example, I would venture to say that most parents do not tip ski instructors when they pick up their kids from an all day group lesson. That has been my observation after dozens of pick-ups.
I think it may not be correct to put all mountains under the same umbrella. The local and drive-to mountains like Jiminy Peak charge significantly less ($300 for a six hour private lesson), while the overnight mountains like Sugarloaf charge more ($420 for full day private) and the fly/destination resorts like Deer Valley charge the most ($950 for a full day private).
In my experience, prices are high, at least at the mountains we ski. The last three mountains we visited - all in New England - had full day lessons priced between $750 and $900. I've taken tennis and golf lessons at some of the best resorts/clubs in the country and the cost is significantly less than that. We've hired fishings guides, mountain biking guides for the day and the cost has been 1/2 of that.
I am not sure if lowering the prices would be such a bad idea. Our family has taken over 50 lessons in the last 2-3 seasons and not once have we been turned away because it was full. And, I have spoken to many, many people who would love to take a lesson or enroll their child in ski school but can not afford to do so.
I have not seen any data that shows which of those three "groups" does the most lesson business, but my hunch is that it is the destination resorts given that they tend to attract the most affluent skiers (both % and number-wise) since it costs much more to take a family of five skiing for a week is Aspen Colorado than it does at Hidden Valley in Missouri.
I think the biggest driver behind lesson fees, at least at the larger mountains, is that the mountains are usually part of a season pass and they are trying to "make up" for any money they left on the table with season pass holders. As it has been written about here - the season pass business is largely based on both getting more skiers on the mountain but also more revenue per skier (either by enticing them to spend and/or by raising prices - lessons being one such example).