I've got one of the Nazi-marked HP's also. Mine has been reblued sometime in the past but still, it's a $500 pistol easy. If your's isn't reblued and the markings are genuine, you're looking at anywhere from $600-900 depending on condition. Be aware, if you shoot one of these, it doesn't have the mag safety of the newer guns. Extractors also break in these age guns and can be a bit of a hassle to find.
The Browning Hi Power is one of the most popular handguns of the 20th century. It is the only firearm that was manufactured and used by both sides during WWII. There have been good and not as good built under various arrangements over the years.
It was my first centerfire handgun and after numerous other tries at something better, is again my principle handgun.
Forget the responses above.
It's worth at least $225.00!!!
I'll be over right after dinner to pick it up!!!
A serious answer to your question:
According to the 2008 Standard Catalog of Firearms (18th Edition), a German military High Power produced in the Belgium plant (should have a "ch" production code, is worth $450 in "very good" condition. Captured pre-war commercial versions (look for WA613 Nazi proof mark) are listed at $1400 in VG condition and $1150 in Good.
Gun Traders Guide lists a war production model like yours at $653 in Excellent and $467 in Good condition.
As with any collectible, condition and markings are critical. Yours appears to be a Nazi wartime production which seems to run in the lowest price range.
The High Power (early production was known as P-35) is a fine pistol, my favorite too. It was John Browning's last design, which actually was finished by one of his co-workers. He thought of it as an improvement over the 1911. I carry a Charles Daly clone and have a newer Browning "Practical" series in 40SW. Both are dependable and accurate. If nothing else, it's a fine shooter. Wish I had some cash on hand.