For many years impecunious British Alpinists camped on this field just outside Chamonix. It wasn't an official site. The field was owned by M. Snell, who owned the Snell Sport shop in Chamonix. From time to time the Gendarmerie would raid the site and move people on. For a few days people wold migrate to the woods outside Argentiere before slowly filtering back to Snells field. If you had gone off climbing and left your tent on the field the police would sometimes "arrest" your tent and take it back to Chamonix with them. You would then have to go down to the gendarmerie and ask them to give it back to you.
Just opposite to Snell's there was an "official" site called Pierre d'Orthaz. The owner was very nice and just charged what he thought you could afford to pay. A couple of people even got to stay for free.
I haven't been back to Chamonix since the mid 1990's and I understand that Snell's field has now been built over.