from decimal import Decimal

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

    def _get_context_price_list_line(self, party, product, unit_price, quantity, uom):
        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()