I binge. Or purge. I forget which one means you doing in large amounts every once in a while.
Example: I purchased the entire Urusei yatsura collection. I mean all of it. All of the manga. All 195 TV episodes. The OVA. The six movies.
Same goes with patlabor. And Card Captor Sakura. And Tenchi Muyo.
Essentially, if I like a series enough, I'll get the whole damned thing within a month or two. This is due to some tramatic childhood experiences. Specifically, I wanted to buy a game for my Saturn back at some point in the 1990's, but I was poor and had to save money, and by the time I had enough money, the game was no longer available (i.e. Saturn died).
That game was Panzer Dragoon Saga. many of you may not be familiar with it, but it sells today for about $230 (check google).
So, to answer the question, i spend a few hundreds every couple of months, like every 6-12 months, depending if anything catches my attention.