I have a suggestion: Perhaps you could build some kind of e-mail alert system that lets me know when there's an e-bay "Buy Now" item available within a user specified price range. You could also let me know if there an item I want is still within a certain price range hours before the bid closes.
EDIT: Typos.
I'm guess a stats nerd so I like to see that stuff haha.
I like your feature suggestion, just put it in my product backlog.
They are simple and obvious, the only feedback I would give is that I would think (not being a huge ebay person) the current charts might actually be changed up a bit. I would be more interested in seeing the clustering of prices, or something like how long the listing has ran without a bid (indicating more likely desperate takers and the like). If the current charts do influence the price in some way that can be used that is advantageous to the buyer, then I would rescind my comment.
Sent this site to a few friends who don't read HN, they are highly appreciative.