I found that as I started my hobby I spent a good deal more then when I have since then. The original costs of equipment really put it up there. I began keeping track of the fabric, batting and threads as those can be compared month to month and felt better about what I had spent. Really you buy the rulers and mats some, but they would not be considered consumables of the hobby -they are the tools.
In the long run I think you can give yourself a break and just know that beginning it will be a bit more. If you look at what you saved making the placemats alone you are probably already ahead.
I usually budget myself $40 a month for fabric. I buy my batting from JoAnn's with a 50% off coupon and buy a full bolt at a time - it really lasts! Those kinds of things will help you keep a lid on the expenses.
Happy quilting and sewing!