I snowboard and my fiancÚ skis. We are both gear whores so we have a lot of different outerwear over the years. This may be generalizing and just based upon my own observations a little too much but I think a difference between snowboard and ski jackets is design and construction components based upon needs for range of motion related to each activity.
Snowboarding jackets you mentioned tend to be more often than not technical shells designed to allow a broad range of motion used with snowboarding. As such, they don't generally have much bulk added through insulation.
Skiing jackets you mentioned tend to not have to accommodate the same types of range of motions used in snowboarding and therefore have different cuts. As a result, they tend to have more freedom in design to add more insulation, etc., that would not negatively impact a skier's form/function/range of motion. This adds to the cost... generally.
Or maybe they know the target market for snowboard gear is teenagers and ski gear is for their parents who have the money. ;-)