Valuation of non monetary consideration: equivalent money value must not be less than the cost of providing the service. Where non monetary consideration for a taxable service has an unascertainable value but a market amount for a similar service exists, Rule 3(a) fixes taxable value as the gross amount charged for that similar service. If no similar market value is available, Rule 3(b) requires the service provider to determine the equivalent money value of the consideration, which shall not be less than the cost of providing the service; cost measurement methods such as Cost Accounting Standards may be applied to establish that cost floor.