There are quite a few reasons I buy a lot online. Aside from saving time, gas and my sanity ( two if my three kids are not great shoppers) FREE shipping supplies are a huge perk.
This is a deal I just got on my favorite multivitamins. I scanned the old jar with my redlaser app on my phone and saw that the best deal was online. It came two days later with these two fab boxes and some much needed air pillows.
If you sell online and have friends and family who buy online but don't sell online they might be a great source of free shipping supplies. I try to use these boxes for First Class shipping and get free Priority boxes from the PO ( also shipped to me for free) for my Priority mailings. I'd say I do half FC and half Priority. Every once in a while I have to buy a big box for an Amazon shipment but I can't remember the last time I had to get one for EBay.