So, um... I managed to pick this one up at the Swedish equivalent of eBay a couple of days ago.
It arrived in the mail today. I paid like 40 Swedish Kronor = 6 $ for it. The box is not in the best shape
(got a sticker on front, and one on the back), but the cart and manual are in mint condition.

As far as I know it is pretty rare, but what do you guys say? And how much do you think it is worth (roughly) ?

I say you are looking at between 100 & 150 euro. Nice score. That game is a lot of fun to play if you like shooters!

Yeah, it actually had nice gameplay when I tried it out .

Yeah these never, ever show up. Good find! Definitely something worth holding on too!

Yeah, I was surprised that I won the auction without the slightest competition, but then again, I guess there are not as many GBA-collectors residing here in Sweden as there are in other countries. I also think this game is relatively unknown.