I don't spend any out-of-pocket money on records right now; I've been only spending money that comes in from selling records I don't want anymore. Therefore, the monthly spending amount varies. I'm working on shrinking and tightening my record collection.
EDIT: my last "big" month of records currently is september with I believe 7 or 8 records coming in. I'm gonna set a goal to keep this to be my last month like that and keep the amount of records coming to around 3 or so.