Both transfers to Modlin and from Modlin to the centre for about 140zł (35 Euro) per 1-4 person car. Once you make a reservation through their site the price is fixed regardless of traffic and weather patterns. They will pick you up from the airport, your home, workplace or hotel. Seats for kids are free. Also they will help you with your luggage. You can call them, send e-mail or fill in the reservation form on their web.