Why did the rip-off crew bring narcotics to the site?

Just like in the movie Scarface, there's no reason for the rip-off artists to be carrying the narcotics to the set-up and phony buy. If they had no intention of making a "square deal" than why would they bring the cocaine to the meet? Not only is it unnecessary but it furthers the criminal jeopardy that they would assume if the deal were busted by the law.