I wouldn't doubt it, having recently returned from ten days in the area. Even our roundtrip bus ticket from NCE to the lovely town of Menton just near the Italian border cost over 50 Euros for the two of us. Going and coming we saw some affluent looking fellow passengers disembarking/embarking at the Monte Carlo Hotels. They obviously chose the bus.

I'm guessing that if you have to ask the price of the taxi, you're better off on the bus.

The train is cheaper yet, but involves either a bus or a taxi from the airport to the train station, as I mentioned in my earlier post. Oh, and there is helicopter service from NCE to Monte Carlo, but no air miles AFAIK.