200-300% on livestock is common, even higher on freshwater... those $2.99 mollies probably cost 30 cents.
Mind you, that's above WHOLESALE prices. You're _not_ paying wholesale at BRS or Marine Depot or LiveAquaria. You're paying retail, albeit at a discount store. Those online stores sell for a good deal over wholesale as well.
I support my LFS's. They provide several services that are difficult to do without. Frozen foods, for instance, are much easier to pick up locally. Shipping... LFS's pay shipping on a truck load, it's much cheaper than paying for a 100lb box delivered to your house, and much less likely to have been kicked around the FedEx office for a few days. Even paying tax, and markup, it's still sometimes cheaper to buy big heavy stuff locally. Being able to see a healthy animal _before_ you plunk down your cash... that's a service that I'm willing to pay for.