I can always justify spending money on crafts. At the rate I buy supplies I figure every card i make cost about 34.00. Pleasure and enjoyment- priceless. I have a monthly bdget that I allow myself- i TRY to stick to under a 100.00 for all craft related stuff. That include paints, materials, tools and for things like crops- and food that I might buy there. I also include in that budget all my kids crafts.
One way I keep track of how much I spend is a use a PayPal debut card- you could l also use a pre-paid card. or rewards type card where you get credit card gas rewards or air miles.
My PayPal card works perfectly because the only way money goes into my Paypal account is when I sell something on ebay.
It has helped quite a bit with budgeting.