My favorite purchase is very old...
There used to be a store in back of the castle that sold "original production cells" and they were like buying lp's..you would flip thru till you liked one and they were cheap (maybe $20-25). Then Disney got smart and called them "art"..framed them and sold them for big bucks. Here's one from my collection.
1st Fantasia original pencil sketch of Cheernabog...
TIBM is another of your favourite purchases from WDW.