I am flying from Paris on a two week holiday. The parking fees at the airport are quite expensive. Does anyone know alternatives?
Consider one of the nearby hotels.
Parking is available at all 3 terminals at Charles de Gaulle.
Long term rates are 22€ per day up to eight days and more expensive with a longer stay. This is presumably what you've seen, and certainly for two weeks, that'll hurt.
If you are planning a longer stay it may be advisable to park at one of the nearby hotels who offer great deals on park and stay: these include the Hilton, Novotel, Ibis, Prestige, and Sofitel.
Why don't you take the train to the airport? Less risk of missing the flight because of traffic jams, detours, sudden snow storms or construction sites, and you can leave your car at home where you don't have to pay parking fees.
I disagree that "the parking lot looked really secure, i.e. cameras, fences, security officers" makes your car safe. There are maybe 2-3 underpaid guys in a booth who have to look after 2000 (or possibly more) cars. What do you expect would happen if they see someone breaking into a car on a monitor? It makes no sense to run after them because if they watch over such a large area it can easily take 2 or more minutes to get from the booth to the car, and even if they get there i don't believe they would get into a fight with the thieves for minimum wage.
Have you ever seen real security camera footage? It's quite useless to identify people in a crowd, unless you wear a sponge bob costume or stand out in some other way.
It's difficult to find something really cheap that isn't too far away from the airport. I once used Aerpark and it seemed to be reasonable for me. I paid 70 Euros for 7 days. I think 10 Euros a day is not too much for close-to-air-port parking. The good thing is, you can make your reservation online and the parking lot looked really secure, i.e. cameras, fences, security officers etc.
To get to the airport there is also a shuttle bus service available. Some years ago it was included in the price, but I don't know how it is today.
So for two weeks, you should probably expect to pay 140 Euros, but maybe there is a reduction for the second week.