I can't really comment on this particular one because I have no experience with it, but I'm really skeptical about the 500 mg/hr claim. I don't think it can be real. If it is real then the price is certainly right. I have a feeling this ozonator falls in the category of "made in China ozonators" so I would be careful if I were you. I have not experienced any Chinese water ozonators that have lived up to their claims or their warranty.
Just for the record, any amount of ozone is possible from dry room or atmospheric air. Large commercial ozonators used to treat sewage in treatment plants produce 1000 pounds of ozone per day or more. Dry atmospheric air is the feed gas for these types of installations.
The pump is usually the first thing to fail on most inexpensive water ozonators, especially if made in China.
Hope this helps, and best of luck with your decision making