Everything is collected by someone somewhere
http://www.ehow.com/how_2241624_go-pebble-hunting.html
http://www.thingsmagazine.net/text/t17/pebbles.htm
At least it looks like it's inexpensive for now.
Unlike this other beachcombing activity. I read an article recently that said a bit of red glass had sold for $500
http://www.seaglassjournal.com/index.htm
Steve B