@Dreamer I have been unable to reproduce the result you stated in your post.
Note that if you only enter $0 for beginning inventory and $4500 for ending inventory, your COGS will be ZERO. You most likely need to enter the cost of items you sold during the year as Purchases.
Regardless, if you are using the proper version of TurboTax (Self-Employed if online or Home & Business if desktop) and also indicated that you have an inventory to report, then the COGS should be calculated for you.
