You are assuming that the raw cost of the chips are 100% of the cost of selling one to the consumer. Other costs are fixed like quality control/testing, market

You are assuming that the raw cost of the chips are 100% of the cost of selling one to the consumer. Other costs are fixed like quality control/testing, marketing, delivery, overhead for the distributors profit, etc. I'd also expect RMA costs to be lower since you can be sure which DIMM is bad, and that it's not CPU, CPU socket, motherboard, powersupply, etc.