from decimal import Decimal

class PriceList(ModelSQL, ModelView):
    _name = 'product.price_list'

    def _get_context_price_list_line(self, party, product, unit_price,
            , dealer_price, quantity, uom):
        '''
        Get price list context for unit price

        :param party: the BrowseRecord of the party.party
        :param product: the BrowseRecord of the product.product
        :param unit_price: a Decimal for the default unit price in the
            company's currency and default uom of the product
        :param quantity: the quantity of product
        :param uom: the BrowseRecord of the product.uom
        :return: a dictionary
        '''
        context = super(PriceList, self)._get_context_price_list_line(
            party, product, unit_price, quantity, uom)
        if product:
            context['dealer_price'] = product.dealer_price
        else:
            context['dealer_price'] = Decimal('0')
        return context

Pricelist()