I was thinking about that. What about an asterisk? Then you could make the tooltip the asterisk expansion. On the bottom of the page, you could also give the expanded version.

This might be the best of both worlds, because you can keep the wording but you also let people know there's more information about what it means.

EDIT: Another idea...

So, you could make the price plus the "x left" be a single graphical unit, thus strongly tying the "x left" to the price, rather than to the seat selection. Then, right below that in a light font, you could say something like "12 left from $y to $z".

So, as an ASCII art example: http://pastebin.com/tS8MPeXK

We've pushed out some fixes to the design -- thank you, for your feedback, it was quite helpful in helping us think through the redesign.

http://bit.ly/y3uvv0

Great suggestions, thanks a ton for taking the time.

We'll be making some changes to it very soon and we'll post details once the changes are live.