There’s no such thing as an 8gb ipod touch 3rd gen. Apple and the sites that sell them lie and rebadge leftover 8gb 2nd gen touches as 3rd gen. Or they’ll say something like “8gb ipod touch, latest generation” which is vaguely true in a slimy, deceptive way in that the 2nd gen ipod touch is the latest generation for an 8gb model. Or at least was at some point in time - there appears to be an 8gb 4th gen.
So your model doesn’t have the increased speed, increased ram, etc. of the third generation. and you’ll have to factor that into the pricing. A quick perusal of completed auctions on ebay suggests they sell for $80-120 depending on condition. There are some sales you’ll see for units at $150+, but those are old stock new in box sales.
I’d say you could expect to get $100 on ebay or you could try craigslist.