The cheapest way to get from JFK to Inwood is by using public transportation. Here are the possible solutions:

1. Public Transportation:
– Take the AirTrain from JFK to Jamaica Station. The AirTrain operates 24/7 and costs $7.75 per person.
– From Jamaica Station, transfer to the subway and take the E train towards World Trade Center. Get off at the 168th Street station in Washington Heights.