There are ways to keep costs down in quilting - you can shop only clearance tables, yard sales, thrift shops for your fabrics; you can salvage old clothes, etc. Batting can be another old blanket or quilt, like our foremothers did. A lady in my quilt guild buys inexpensive blankets at Costco that serve as both batting and backing for her quilts - they turn out really nice and cozy and it's cheaper than buying batting and backing. Maybe not technically a quilt since only 2 layers, but they're well-made and warm and the charities love them. (And happily, nobody in the guild goes all "quilt police" on her about it.)
I track and budget my hobby spending but it's one figure that covers everything - thread, rulers, fabric, machines, sewing room furniture & decor...all of it is one lump sum that is in my budget. I have a very strict budget for every dollar I earn...it's not particularly limiting but I stick to it like it's a law. As long as I stay within my budget I can buy whatever I want! If I want something big or want to go on a spending spree I just have to save up for it. Of course, that's barring unexpected expenses like the nearly thousand dollar dental bill I just got from replacing a bad crown - ouch! (literally!) I'll be on a fabric diet for a little while until I catch my savings account back up, LOL.