routingParams.departure не влияет на

Вы почти правы, просто добавьте это:

def hotel_cost(days):
  return 140 * (days - 1)

def plane_ride_cost(city):
  if city == "Charlotte":
    return 183
  elif city == "Tampa":
    return 220
  elif city == "Pittsburgh":
    return 222
  elif city == "Los Angeles":
    return 475
  else:
    return 0

def rental_car_cost(days):
  cost = days * 40
  if days >= 7:
    cost -= 50
  elif days >= 3:
    cost -= 20
  return cost

def trip_cost(city, days, spending_money):
  return rental_car_cost(days) + hotel_cost(days - 1) + plane_ride_cost(city) + spending_money

city = raw_input("where are you going? ")
days = int(raw_input("how many days are you staying? "))
spending_money = int(raw_input("how much spending money are you bringing? "))
print trip_cost(city, days, spending_money)