If we're counting minis or Magic cards as an entire purchase, those have got to be the dominant factors, right?
Single item? Probably a box set or collectors board game in the 200+ dollar range.
Single project, but not a product? Probably everything I've purchased so far for the as of yet unfinished game room and table in the new house. 6-700 dollars and growing.
Three Warhammer armies circa 1995? Around a thousand dollars easily.
Almost 30 years of pretty much non stop Magic Card purchases? Haaaa...