I would not want to skimp on stabilizer. Have you made t-shirt quilts without it? I think AStitchintime above me is correct that inferior materials are going to translate into more time investment on your part to get a passable end result.
Another idea to consider -- if people are reluctant to pay what you need to charge for quality materials in a tshirt quilt, what if you offer them other cheaper alternatives-- pillow covers, smaller wall hangings, throws with tshirt motifs foundation pieced to fleece, even baby clothing or hats made from special t-shirts. Keep the actual quilt a quality item, but make cheaper novelty fun things that those who can't or won't spend on a full quilt can enjoy.