AT a minimum, the A-bomb probably saved 10,000,000 Japanese lives.
It also saved Japan from a civil war since most likely the Reds would have controlled half of the country, when the Soviets got into the fight.
An invasiion was not necessary thus your (highly dubious) million dollar figure could have been reduced to zero AND the bombs could have been avoided.. We could have agreed to a conditional surrender at the outset (as Truman finally did) to let the Japanese keep the emperor. Sorry to burst your bubble but it was not necessary to INTENTIONALLY kill thousands of babies, Christians (Nagasaki was the heart of Japanese Christianity), and little old ladies to promote terror.