I was advised during my recent patrol training that 8 years of attentive advancement is considered the minumum "development period" for personal skiing skills.
You can learn to do first-aid and handle a sled in a year.
As others have stated, ski days and miles are required. Boldness to go into "uncomfortable conditions" Is required to gain experience in those conditions. Tree skiing is a great tool.
Young people have the advantage. My 9 year old son looks like mercury on the slopes and rides the steeps, trees and bumps with confidence.
The big price is the time. If you need to ask the $$, you cant' afford it
Good second hand ski's are fine.(keep 'em tuned) Good boots and fit is required ($700).
The payback Hmm...
The thrill of speed. (relative, tree skiing can be quite slow and still feel "fast").
The whole mountain becomes yours,
We are having a crappy season here in the east. I was aware on Saturday, that I could double the available terrain if I just lifted one ski off the "surface".(humor) The feeling to be able to do this is part of skiing well. The soft snow at the edges is yours.
Drops and narrow stashes beckon.
There is no favorite time or place.
If you like it, it's worth it.