I'd label that vise "medium duty". The swivel lock handle is clearly bent and the seller shows it. What he doesn't show well is the main handle. Is it bent as well? To me, a main handle bent on a medium duty vise (or any vise really) is a real concern because that torques the whole vise out of whack (trying to get it to do something it was not engineered to do). The jaws look pretty straight...
$40 is "fairly fair" if it's in good shape. It's not a heavy duty vise though just so you know...good luck!
If you really want a vice that small, then it might be worth it. I think he means the jaw faces are in good condition, the jaws themselves have suffered grinding damage.
I think $30 is okay. You can do better, but you'll have to be much more patient. Sometimes buying now for $30 is more worthwhile than waiting 8 months to buy at $20.
I personally would be more happy spending more to get that Parker that bczygan posted.
Oh heck, this is GJ...You should get the columbian, the Parker, and the prentiss!