Some believe the OD is now a collector's item and that's true only in that they are no longer made. But I sure wouldn't pay $1000 for one.
I would say maybe as high as $700 but I consider that high even for a NIB.
I would more consider the caliber for collector value, and would suggest certain calibers might bring a better price. For instance, I have a G20 OD and believe that might bring more down the road than, say, a less popular caliber like a GAP or even a more popular .357, maybe. Then on the other hand an OD GAP may be a big deal in 30 years, who knows.
But one thing I don't believe is that a gun will really jump in value until it's 100 years old, or something like that. At best, I expect some guns to hold their value and maybe increase, like a Colt 1911 or something like that.
Bottom line, I don't put extra value on a Glock just because it's an OD.