Myoko Shuttle offers direct transfer from Narita & Haneda airports with three shuttles per day. This is the cheapest shuttle service available, and the route also stops in Madarao and Tangram.
Narita/Haneda : ¥10,000 one way
Booking is now open for this service.
Nagano Snow Shuttle have been transferring people to and from Narita and Haneda for many years and were the first dedicated airport shuttle service in the area. They are an established service and offer up to 4 buses a day which can very convenient depending on when you land. Most services require a change of shuttle in Nagano.
They also have daily shuttles to and from Hakuba and Nozawa Onsen.
Narita/Haneda : ¥10,200 – 12,400 one way