Go through your results for flights to Monte Carlo in France with Netflights.
If these flights are too expensive, try searching for a different time of year. So if your dates are flexible, consider looking at different times of year.
So, if the flights to Monte Carlo don't work for you, you could always try searching for flights to other airports in France.
Looking at a few different departure airports will give you even more choice. See what you can find. And remember, it's best to book your flights in advance wherever possible.