I do believe the Prismacolor are worth it, however I have the crayola ones for our youner children (7 DS, 6 DD, and 2 DD). I will let DD6 use the prismacolors in her nature journal, depending on time and location, but not 7DS or 2DD (b/c they are just not ready).
I justified the cost by buying them as part of our Christmas gift one year. We do not spend much at all on Christmas, but this was our big family gift (I paid $50 for a 36-pencil set at JoAnns with coupons). I then purchased sketch books for our children to receive as individual gifts.
As I said in the other thread, the pencils are literaly going away (we have used them down to nebs for some; we have not had breakage issues but just sharpen them over and over and use them all the time). But we’ve had them since Christmas 2010, so I feel they have been worth it.
And no, Crayola is not even a comparison. You can see a big difference in quality, but we have those for the younger children and we take those when we travel with colored pencils in hand.