Notional interest on advance deposits: include in assessable value only where deposit influences sale price or yields quantifiable benefit. Inclusion of notional interest on advance deposits in assessable value requires a demonstrable nexus between the deposit and sale price; notional interest may be added when the deposit results in lower price or special discount to the depositor, or when two distinct prices create separate buyer classes, in which case the manufacturer's benefit must be quantified. If no price difference or evidence of price reduction exists, notional interest cannot be added. When interest credited to the buyer is below normal bank rates, the shortfall represents the manufacturer's benefit and must be quantified and included.