'Pawn Stars' -- Mayweather Loss Would Be HUGE For Vegas

The guys from "Pawn Stars" can spot a money making opportunity from a mile away -- which is why they believe a Mayweather LOSS would be HUGE for the city of Las Vegas in the long run.

Don't get it twisted ... Corey and Rick Harrison -- who were hangin' at the D Hotel -- told us they're rooting for the hometown guy, Floyd Mayweather ... but explain why Floyd taking the "L" would be MUCH BETTER for Sin City.