Personally, I have never thought of watercolor as a "lessor" medium but
perhaps others have. I have always liked the etheral quality of the
paint and the texture of a really good paper. Perhaps the price issue
comes from the fact that in many cases a watercolor can be completed in
a shorter amount of time and the artist may produce more prolifically.
Materials for this medium are more easily procured and also more
portable-oils/ acrylics need more set up, thought and planning.
Just a thought.