As far as I understand it the ex-works concept can be a means for the dealer to regain some of what you have bargained him down. It would therefore be wise to get details of the additional costs involved before starting to haggle.
Always haggle with a dealer.
You could find for example that the price is €21K plus €750 costs. However, if you were to bargain him down to €20.5K, you might find that the costs had creeped up to €1K instead. If you establish the costs in advance this shouldn't happen.
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