La Compaginie is running a realy nice promotion now. You fly from New York (EWR) via Nice in business class plus a helicopter flight to Monaco for 1598$.
We found the cheapest flights in October, if you want to book don't wait to long as there are not unlimited seats available.
The only downside is that this deal is not available on that many dates, and flights to Nice are operated by the older Boeing 757 and not as flights to Paris by the new A321neo.
But on the other hand you get an amazing deal, their business class is much better as economy or premium economy class on other airlines AND you get a helicopter flight on top of that for 1598USD !!