I think they're a little collectable, but I'm not sure if they're worth much. I have a few I'm keeping too, so I guess that makes it collectable. :-)
There are probably a few Amiga fans that would give a few dollars and postage for one, but if you got an offer for more than $3-4US, I'd be suprised. Now in another 20 years, who knows, you might see them on Antique Road Show or something.
Here's a picture of what you're probably refering too...
Amiga PenPlaz