That JW MWS i think is actually pretty spot on for prices.Second up...expensive kit, but not really all that much else to attract someone. Maybe if it came with the original parts it would be worth that, but currently you can pick up one of these kits second hand in the UK for £500 all in, so hardly seems worth it.
I havent seen that kit for sale for a while, and with the extra's it is pretty close to the £1k mark.
Problem with selling airsoft stuff - the more expensive it is the smaller the pool of buyers. Go to a car boot and the guy selling a used Cyma will have people checking it out all day long. But something like a DAS, or this, it will be only of interest to someone looking for it, or if it's an absolute bargain.