For the purposes of this Directive, ‘open market value’ shall mean the full amount that, in order to obtain the goods or services in question at that time, a customer at the same marketing stage at which the supply of goods or services takes place, would have to pay, under conditions of fair competition, to a supplier at arm's length within the territory of the Member State in which the supply is subject to tax.

Where no comparable supply of goods or services can be ascertained, ‘open market value’ shall mean the following:

(1) 

in respect of goods, an amount that is not less than the purchase price of the goods or of similar goods or, in the absence of a purchase price, the cost price, determined at the time of supply;

(2) 

in respect of services, an amount that is not less than the full cost to the taxable person of providing the service.