There are Error Tokens to be found for under $10. I recently picked up a couple of error tokens from The Reserve for under $2.00 each (postpaid).

So with that said, I wouldn't think they would sell on eBay for more than $10 - $15 each.

I wished there was a market for casino tokens.....but my guess there are less than 250 collectors who activity collect casino tokens.

I still pick up tokens off of eBay for under 50 cents (in NM condition) usually when buying a lot of tokens.