I'm going to agree with the other posters here. I've sold a few items on eBay, and purchased a bunch. I've noticed that individual items will sell at a higher (relative) price than bundles. Most people that are looking for oop or used material already have some and don't need a whole collection. This even holds for lots of 3 modules or magazines. The individual sales will bring in a higher aggregate amount, albiet with a bit more work on your part. Also, pictures and condition are critical. If there is no pictures, I tend not to bid. If there are no other similar items being offered, I may bid, depending on the feedback level of the seller, though will assume it is in poor condition.
FYI, the shipping seemed a bit high too, though I don't know the gross weight of the books. Priority shipping costs $3.85 anywhere in the US for a FedEx sized envelop. Media mail is pretty cheap. Items that are listed with overly high shipping & handling fees (why should I pay a handling fee?) also tend to be discounted.
So, anyway, although you may get someone that is looking for all those books and will pay up for them, chances are that there a number of people looking for just one, and is willing to pay for only that one.
--Sam