It will cost you £550 (no VAT) for the use of 1 bike for a maximum of 10 days riding.
Boston Bob, your guide, airport pick up, mechanic, fixer, translator, shrink and knower of all things will cost you $250 US dollars per seven days per person. Any extra days will be charged at $150 US dollars a day divided between all riders. As I write this (1/1/18), flights to Boston, return, can be found for £320, but this will vary depending on what time of year your planning on going.
You will need insurance, and we will need to see proof of this when you pay for the bikes. Normal holiday insurance will NOT cover you for actually riding the bike in the US. They will cover you for being on holiday with a motorcycle but NOT actually riding one. So if you hit something or someone, you will have to pay, alot. Dogtag.co.uk are the only company we have found that will provide the insurance you will require. We have no commercial relationship with them but highly recommend them. Sorry, but you will need insurance in place before you can use our bikes.
Fuel is around $15 a day depending on your mileage. Accommodation can vary from nothing in some camp sites to $100s or more for hotel rooms, depending on your tastes. Having travelled extensively in the US, on average we usually budget $40 per night per person for great B&B's, hotels and motels, accommodation is not expensive in the US.
Food and beers and souvenirs, again, this is a personal choice but $60 per person per day would usually cover it.
So with ALL of the above factored in you could have an amazing 7 days in New England for approximately £1750 per person. We can guide you and help you organise all of the above, if you've never done this sort of thing before.