Well, the gun shop is wrong. Please provide pictures of the holster, so we can see it. Holsters on e-bay go for anywhere from $50 for a beat up one, to $200 for one in really, really nice shape.
A matching magazine adds around a $100 or even more to a gun.
Your loading tool is also worth from $25 - $85, all depending on how it is marked.
Here is a link to Simpsons they have many lugers, but remember this is retail price, with all matching, and no reblueing to the gun. A reblued luger is worth around the price they stated at the gunshop for the entire kit.
http://www.simpsonltd.com/LugerRoom/...ser_lugers.htm
Ed