Yeah, $100 for a L173 would be crazy cheap from what I've seen, but I don't think L173 based on your photos. For one thing, I've seen them white, off-white, or a sort of pale cream, but always more pale than yours looks on my screen. Also, you can't see enough of the pattern on the body to take a shot at it being L52 vs L333 or something similar.
But to feel better making a decision you might want to get photos showing the whole fish-- also those left at the shop if you can-- then maybe post them over on planetcatfish, which has a section specifically for help with IDs.