I have a couple, and they both are, and are not "Lugers". Luger written on the gun, legal rights to the Luger name, a toggle action (yes, its blowback), and a general resemblance to the P.08. But other than the toggle, mechanically quite different from the Pistole Parabellum. But it IS a Luger, technically, anyway.
They are not top of the line guns, being framed with cheap alloy, but they are not total junk, either. They are fun, even though the sights are not the best for precision (like the real Luger in that regard).
$200 in good shape is what they are going for lately around here, may be different other places.
The Erma is long out of production, there are NO parts available, and it is also mostly a cheap alloy. $400 price on the last one I saw, and I passed on it.
$600 for a worn out barrel "shooter" Luger is high, but all Lugers have had price jumps lately. Mostly due to the dollar's purchasing power dropping, not due to any change in the supply.