OMG, that is ridiculous, but to be honest, I prefer a big box to plastic bubble wrap and Jiffy bags. It still seems crazy, though. I always hate ordering small, inexpensive things through Amazon because I know that gas for the delivery truck to get way up here far exceeds the price of the cheap whatever-it-was I had to have.
You could use the boxes to help you expand your garden. I don't rototill (we don't have one), and I can't find people to do it. So I do the lasagna method of laying down cardboard, wetting it down, topping it with layers of organic matter/compost, topsoil, leaves/grass clippings. It takes time (I did it in July and won't plant in it until next May/June) but it's a good use for cardboard, and a pretty easy way to start a garden.