I guess I have to ask how much you are paying for the other stones you are buying now? There may me cheaper, but if the machine is giving you 10 - 30% upside down stones (USD) using them, then is it really worth it? My last order of Ioline stones were priced at $149 for 500 gross for the 6 and 10ss crystal stones. That works out to .002 cents per stone. That is a bargain in my mind.
Using the 10ss crystal Ioline stones, I have had maybe 1 per 1000 USD. The 6ss is around the 1% range. I haven't used their colored stones yet, but I would expect the same good results.
Good luck