All Lugers are collectors pieces now.....
What varies is the degree, and price.
Lugers with the finish gone are in the $800 price range, and it isn't going to go down. Refinshed guns are also in that same price range, or more. I have an absolutely beautiful 1936 Mauser S/42, factory refinished (so I was told) that I got for about that last year. It looks brand new.
Guns with some fair amount of original finish left are around twice that much. Rare variations (and there are a lot of them) can be 3 times as much, or more. One 1917 P.08 at the last gun show I saw was $1600. Fair condition. An Artillery model was $2200.
The last P.08 Lugers were made in 1942, when Nazi Germany stopped production. Mauser made some in the 1970s, using the Swiss pattern frame (1902 model), and you can sometimes find these in new/like new for around $8-900. Erma made some .380"baby Lugers" back in the 60s-70s, but these guns have some aluminium alloy parts, and don't hold up well. Also repair parts are nonexistant. Stoeger made some .22LR "Lugers" (I have a couple) that are fun, but are not true P.08 replicas, even though they do use a toggle action. They are Lugers, because Stoeger owns the rights to the "Luger" name in the US.
P.08s have a reputation for being finicky about the ammo they need to run reliably, and a lot of US made ammo doesn't work well. They have poor sights for any practical use, fair to poor triggers too. But they are a really neat piece of history, and a lot of fun. Expect to spend the best part of $1000 for a decent shooter, in today's market.
Just FYI, the most valuable single handgun existant today is a Luger. The single surviving .45ACP Luger made for the US army tests that eventually resulted in the adoption of the Colt 1911 as our survice pistol. Last time it was appraised, it was valued at a million dollars!