I think that is a fair price if it is functioning. If you intend to shoot it, depending on when it was built, it may have been made for black powder cartridges only, something to consider. Also, it takes the .32 S & W (or Short, not Long), which is not a common caliber. Modern ammo in this caliber is loaded light, so it is probably not an issue...just food for thought.
These are very interesting little guns. They start growing on you after awhile. This is a 1921 shipped third model. I think $100 is very reasonable if it is mechanically decent.