you see zone chat and how many people are spamming their purple recipes for sale?
that indicates they are pretty common, enough so that people use one then hock the rest.
last time I bought a purple recipe, I told the guy "ill take it for 500g if you are looking to just get rid of it, but I don't need that recipe" and after some back and forth COD'ed it to me for 500g....
I then picked up that same recipe within 4 hours.
Those purple recipes are common...just wait for one to drop if you don't want to deal with people who pretend its one of the most rare and highly sought after items in game.
Remember people use to do this with standard motifs....and now people will sell the blue ones to anyone who will pay.