In Greek mythology, Charon was a ferryman who would guide deceased souls to the underworld in exchange for a golden coin (the exact cost depended on how many souls went per trip, e.g. it would cost ten golden coins for ten souls to go in one trip).
When the Ghostbusters were in the underworld looking for the shears of The Three Fates, they needed Charon to get across the River Styx. Even though they were not dead yet, the Ghostbusters still had to pay in order to hitch a ride with Charon. They didn't have 20 gold pieces, 50 silver pieces, vase of purest bronze, an etching, nor a Captain Midnight decoder badge. They paid Charon with Winston's rabbit foot and Ray's cheese sandwich. Charon was disappointed it was white bread but accepted the payment. He longed for pastrami, roast beef cut lean, and corn beef. He also appeared to be interested in wheat and rye bread and an outboard motor.