There are more than 5,000 campsites scattered all over Europe, all priced very reasonably. 

Many of these campsites are in areas of outstanding natural beauty. Others are within easy reach of the center of cities like Paris, Vienna or Rome. All campsites have toilets, showers and laundry facilities. Most of the campsites do have a small supermarket, a restaurant, a pub and facilities for social activities. 

You can visit http://www.eurocampings.co.uk/en/europe/ to get an idea.
Another useful link for information on camping is http://www.rollinghomes.com/Elinks.htm.