That is as cheap as I've ever seen them new, but I never see them new any more. I see that Cabelas Gun Library has two convertible 46 LC/ACP's for taht price.
That $500 price sounds like a fair price to me if it is that nice and still has the box. It is what it is worth to you.
Edit:
The retail price is $636 so they should sell new for $500-525.
Dave