First with regards to the active ingredients thing...
Most active ingredients are diluted to extreme amounts in any product forced to list them, I wandered into my medicine cabinet and... well, I haven't got much in there but out of what was there, my neosporin knock-off was 98% petroleum jelly, my hydrogen peroxide was only 3% hydrogen peroxide, my Colgate was only 0.54% active ingredients and this cough syrup sore throat spray that's three or four years old and needs to be thrown out was 98.6% water and food coloring.
So the proportions aren't too far off on the Reptile Relief and I suspect you'll find the other mite products have about the same levels (Although different active ingredients).
Secondly...
I know it's an old thread but I remembered it was made and ended up buying Reptile Relief when the other options I had been considering were sold out...
I bought some sphagnum that must have been loaded with fruit flies (I haven't bought fruit in about fourteen months, so I'm pretty sure it was the sphagnum) and found the flies, when not on my computer screen, were all over the sphagnum and substrate in the Candoia bins and a few other odd enclosures. I figured they were likely breeding in the same so simply threw out the substrate and the sphagnum and replaced it, problem solved. For about 48 hours... then problem comes back.
Assuming the flies were dropping eggs in the substrate and not finding them in any of the other enclosures using drier substrates or any potted plants around the place, I decided to treat the enclosures with a mite spray of some kind and headed out to buy some Provent-A-Mite or Black Knight...
Which the local shop was sold out of (Not much of a surprise, P.E. is open very few hours a week anymore and I was in a hurry so I went to the "other" place nearby... those of you in the Denver Metro area might know what I'm talking about) or didn't carry. I ended up buying some of the Reptile Relief spray (Their store use bottle, frankly I'm surprised they had any left considering the way the floor seems to move with the mites all over the place... then again, maybe I'm not, had they used it, they might not be infested) instead.
So far so good on the fruit flies, haven't seen any since switching the substrates once more and applying the spray. Haven't tried it on the animals since it didn't seem to be an issue and I'm still hesitant, especially on the Candoia, but it seemed to clear up the insect problem I was having and in my past experience, fruit flies can sometimes be tougher to get rid of than mites.