yeah. I did some costing on some parts a while back. And I've heard the same (similar size costing) from some vendors and friends. The prep time is nearly the same, and the parts will turn out nearly the same. but the cost starts out about 50% more on smaller parts, say 4sqft on up until the magical break even point, where coincidentally, prep becomes more meticulous and precise and time consuming.
says me and my limited experience, but I've done some research.