Are you in the United States?
It seems slightly high with a broken latch, but only slightly high. For an eBay price it's probably within the realm of reason. A broken latch on the Aluminum powerbooks or the iBooks is a really pain, because the casing is spring loaded and it will wake up when it springs ajar (unless I'm misunderstanding).
If you're willing to search for a while, I'd look here and on other reputable forums. Also broaden to an iBook 12" if possible, as there are many of those floating around. With respect to that particular PB, it's the very, very first 12" PB, so you should note some of the differences between it and all the other PB 12"-ers -- VGA instead of DVI, an older video card (GeForce 420 vs. 5200, which comes in all other PB 12"-ers and with 64MB VRAM starting with the third revision of the PBG4/12")?
That is... you're talking about this Powerbook, right?
http://apple-history.com/?page=gallery&model=pg4_12&performa=off&sort=date&order=ASC
It's still a great computer, but I'd think that any iBook 12" starting with rev. B and any PBG4 starting with rev. B would probably be better, and they're readily available on forums. However, I would not expect to pick up any of them for <$400 without extensive waiting and looking and / or something wrong with them (as you have here). You might get a fully-functional rev. A iBook G4 / 12" for $350-$400 on a forum.