I'd offer them for 1 Euro ... on ebay.
If you're selling them for a set price then the quality of how you assembled and painted the models determines the price COMPLETELY! You can easily demand 150% for a bautifully painted model or double if it's perfect. If you messed it up and the models look like crap you may have made the models nearly worthless and probably get more money if you remove the colours first. Finally, it will depend on the type of models you're selling. I mean, are they old models, metal or what? People have different preferences regarding different editions so while one guy might give you a lot more for 5th edition bloodhounds of Khorne, another one might not even want them, because he only wants the latest Citadel miniatures available. This is particularly relevant for the Chaos Warriors you're selling.
Really finally: Maybe it's good to get rid of your army before autumn when the new Warhammer armybook hits the shelves and along with that the new models, which might look better than your older ones. Or maybe no new models for marauders and warriors will be released and all the armybook release means is a higher demand for your very army, ie. you could sell it for even more.
Geez, thank god I'm not selling my Beastmen armies like that...