retail, some at discount retail, some at Goodwill or thrift stores, some were gifts, etc. over many years. Selling them would almost certainly bring less than I paid for nearly all of them, thus no profit or "income" but I have no proof of that. Dang. Limiting my options to a garage sale where I would have to require cash (or maybe personal checks?) would limit customers to just a day or two of relatively few locals that would show up at all and even fewer buyers if I were not accepting credit cards. If I donated them to Goodwill or some charity I wonder what kind of tax credit there might be? That is assuming they would take them at all.
I also have multiple copies of some kits I could sell, but although their prices could in some cases be about the same or in others maybe more than I paid, garage sale prices would probably have to be at a loss assuming any kit buyers showed up at all at a garage sale.