1967 Barracuda Fastback rear window

They are not particularly rare and are damn near indestructible under normal circumstances. A good used 67-9 fastback glass should be able to found in the 100.00 range because of the above reasons. What does happen to them is that they are prone to scratches. So look closely at them.
The price you have for a new one seems awfully cheap I've seen them for 4-600 range (couple years ago) when I was looking to replace mine because of scratches, but found a really nice used one.