IMHO (and hoping that if I'm way off base here someone will point it out for me...):
Hide in Plain Sight as per the Shadowdancer is pretty powerful for a level 8 ability. It's probably more balanced at 17th level as per the Ranger... Personally I'd think that shadows are more easy to come by than natural terrain, but that's going to vary.
I'd start by pricing it like the ability was actually a spell. 9 x 17 x 1000 = 153,000gp. That seems way too high, even given that I tend to up the price of non-standard items as a rule. 4 x 8 x 1000 = 32,000gp, which seems pretty low. Maybe x1.5 to x2.0 that value, or 48 to 64K?