From the Standard Catalog of Luger (2006)
your 1917 gun is a 1914 model (produced 1914-18) aprox. 90,000 made in 1917.
grips should be checkered walnut, Original magazines (2) have a tin plated body and wooden base. They were proof marked and serial numbered to the pistol.
Pistol should have a deep rust blue with ejector, mag catch, take down lever, safety and trigger straw colored.
2006 book value for a VG example was $750. The correct period holster with the gun adds several hundred dollars to the value, but I can't tell you how much.
Lugers live in price bubbles, and a $750 gun 15 years ago could be a $1200 or $1500 gun today, sorry I don't keep up on the current market. A $1250 gun with a $400 holster would get you close to where they are asking, so would a 1500 gun and 200 holster..so I'm afraid I can't help much with current value.
Check auction sites and Luger collector sites for more current information on value. And at the auction sites, look at what the guns SOLD for, not the asking prices.
Finding a Luger with the original #'d magazines is extremely rare. All matching except for magazines is more common, but still rare, which is why they cost more. Finding a good condition gun WITH a proper period holster (not a reproduction) is uncommon, so it adds value as well.
$1700 for a good condition WW I Luger with holster isn't drastically out of line, these days. $1200 would be better, of course, but it's a seller's market.
I bought a 1936 that looked new, but was reblued (and not all matching) about 15 years or so ago, for $750. At the time, had the finish been original and all matching (other than mags) it would have been $2200 , or so the dealer said...
Good Luck, I hope you find the information you're looking for.