Sightseeing helicopter flights over Mont Blanc exist. Two operators on the French side sell them: one from a heliport in Argentière, at the top of the Chamonix valley, and one from the altiport above Megève. Flights last 15 to 50 minutes and are sold by the seat or for the whole aircraft.
If what you want is the massif from the air, a tandem paraglider gets you airborne in front of it for about the price of a short helicopter seat, with a pilot strapped behind you. If you want to be over the summit itself, only the helicopter does that — and you book it directly.