IF you have time to make and list an item then you do have time to keep your records up to date.
I keep one simple spreadsheet that lists all supplies that I purchase in the year. I keep track of what was purchased, the purchase date and the total amount. Also how I paid for it (paypal, cash, business credit card, etc)
As for sales, I keep a separate spreadsheet that lists the date the item was listed, production cost (materials + labour), selling price, shipping charge.
When it sells the item gets moved to the 'sold' spreadsheet and I record the date of sale, seller name, etsy fee, paypal fee, shipping that I paid.
At the end of the month its simply a matter of looking at the totals on the sold items to see whether or not I've got enough to pay the bills. Plus I can see at a glance how my sales this year compare to last year.