Here is another selling strategy for webcomic merchandise.
Etsy.com describes itself as "the place to buy and sell all things handmade." They also carry listings for vintage goods and craft supplies.
I recently found a webcomic using an Etsy store. My Cardboard Life by Philippa Rice uses fabric and other assorted materials to build each panel, then turns them into digital images.
With its low overhead, it seems to me that an Etsy store could be an extra point of exposure for some webcomics. Those offering toys come to mind, but original art and t-shirts also qualify.
It an opportunity to attract interest from browsers who might never encounter your main site. Actual sales might be low but it might still generate visitors, where they can inspect your main store. Right now, with low webcomic use of Etsy, comics might stand out, and attract interest for being unusual. Philippa tells me, "T
Here's Philippa's shop . Notice the types of merchandise she's selling. Compare it to the comic: it seems anyone buying one of her books would find the comic appealing.
Two types of webcomic may find Etsy useful: those offering a stand-out version of an item that is already offered by others on Etsy, and those offering comic-oriented, unique items that will be fresh and appealing to Etsy visitors. Comics with a "cute" theme also have potential.
To give you an idea of cost, listing an item is twenty cents.