I'm traveling with some family to Japan in June and I'm trying to iron out my itinerary. We arrive on Saturday night at 11:30pm in HND and plan on flying to CTS the next morning. The flights from NRT are $42 cheaper per person (4 adults 3 children) but all the public transport will be closed by the time we get there. Are there any cost effective ways of changing airports that late at night?

NRT is closed overnight, so even if you managed to get there after your flight from HND (which isn't really possible), you'd have nowhere to go. Moreover, I certainly wouldn't willingly attempt camping out at an airport overnight with three kids in tow. If you want to go ahead with the NRT-CTS flight, your best option is to stay somewhere in Tokyo with easy access to the Narita Express or the Keisei Skyliner trains and head for NRT in the morning.

However, by the time you pay for trains (3,110 JPY per person for the N'EX, for example), your savings will be nearly zero for a huge amount of additional inconvenience.

Just take the flight out of HND. You'd be hard pressed to find anyone that would think making the trek to NRT was worth it to save maybe $10 per person in the end.

A taxi company could probably transport 7 people by minibus for less than 7 bus fares, but I don't think it's worth putting seven people through that for such a paltry saving. IIWY, Id reserve hotel rooms near HND and take a flight from HND next day.