keep records and take pictures-for records and for yourself so you know what you did. You can take off the cost of fabric, thread, batting-not labour or hours spent. A simple way is figure how many yards of fabric used and times it by the cost of fabric. I quilt for charity, I bead for charity, and I am slowly getting rid of all my business clothes-I have only been retired for 10 years-slow, I know!!
Some of the suits were quite expensive-custom made Italian wool for example- but Goodwill sells them for almost nothing. I try to remember that the person buying, needs them and not of the original cost to me. I donate to help others-the tax write off does help some but it is not the be all or end all for gifting.