There is. Just look at the quality of the stuff sold there for 1 L$. It's mostly some cheap shows, know one ever head off, selling hardly creative stuff since it's, like said above, just resell of full-perm items with some cheesy texture.
No quality or popular shop offer demos for 1 (or 10) L$, they all offer it free. Demos for the reputable (and successful) SL shops put the demos for free on the Marketplace. Only cheesy vendors have either no demos at all (which in 99.9% means, their product is crap, badly rigged, not supporting the major mesh bodies or just *****ty textures or it looks like made out of paper) or they charge for demo, which is almost always the same too.
Such lame excuses as that its for redelivery or anything else is just lame. No one wants to gift demos, who ever wants to try it itself just grabs it from MP or inworld. It's just these vendors who cry and complain, that the SL Market is declining, but the reality its just that they never cared to create quality products and now get the bill for it