The cheapest one I found was $110 at http://www.therabreath.com/products.asp?cat=7&pid=128&AffID=2326
It says it is $120 on the website but if you enter the following coupon code: "BTENOZ" then $10 will be deducted from the total. I don't remember how much the s&h was. I ordered mine several years ago and it still works fine. This site also has a free PDF on what you can use your water ozonator for and how long to ozonate various things like fruit (to cleanse), water to drink, etc. It's been a very good machine. I have never had any problems with it and the only things I had to reorder were stones when one of mine broke. (It came with two stones and two tubes).
Good luck in your search -- I hope you find one that works for you and is affordable.