For 2020, The following data is compiled for James Construction. Sales in units for steel, 5,000, Wood 40,000. Direct material and labour cost per unit, steel $3,600, wood $2,600. Manufacturing overhead costs per unit, steel $1,800, Wood $2,400. Pricing coefficient, steel 2.2, wood 1.9

The following information has been provided for sales in 2020. Customer 1 placed an order for 54 steel fences and 25 wood fences. Customer 2 placed an order for 230 steel fences and 420 wood fences. Customer-related costs were $90,000 for customer 1 and $1,310,000 for customer 2

Estimate manufacturing overhead costs per unit were less for the steel fence than for the wood fence. What is a likely explanation for this?