That is not a correct assumption. RDM calculation is based on a ticket price
†Ticket price used to calculate miles earned includes base fare and carrier-imposed surcharges, and excludes government-imposed taxes and fees. Tickets purchased in a foreign currency will be converted to USD at time of ticketing based on the IATA 5-day rate.
MQD is only on fare price.
There is another little problem with the calculator. It is only good for non-stop flights. As it say " *Calculations are accurate for nonstop, round-trip flights only. "