We implemented the multiplier because we are searching for ways to make the game quicker and more competetive. By multiplying all the payoffs by 1.5 and allowing more chances to buy railroads, the game will end in fewer turns. The multiplier feild will accept numbers up to 50, but I assure you that numbers that high are completely unnecessary for real game play. I just figured that it's always fun to see how much you could make with such a high multiplier (ie. from Miami to Seattle, with a multiplier of 50, you would make $1,750,000, enough to buy every railroad and still win the game next time you make it home).
If you're looking for a hands-free payoff chart, check out this Alexa Skill.