It's tough Texas - I'm still leaning towards this is completely legitimate. It'd take a LOT of precise work to make sure that you cut only the glue without damaging the plastic or artwork, and then the mod to the figure itself would take some additional time and would arguably be noticeable unless it was a real pro. The bottom of the box looks almost exactly like 3 out of the 4 or so that I've looked at recently. The bottom "seal" isn't exactly glued like the other sides (at least on several of mine), you can put toothpicks/etc. through the perforations and there's not really any glue on that part (IIRC).
At the end of the day, its your call - but if it turns out to be fake somehow, you should have no problem getting your money back I'd assume. If you pay with paypal and use a visa/mc even if its a debit (instead of bank account #) you can also just file the claim with them if eBay for some reason or another wouldn't work out.
Either way, let us know if you win it. If this one sells for a ton though, I wonder if we'll see some copycats actually trying to forge these and sell them?