I think you can get a gallon for around $35........ it's 99% plain water. That's a fact- I looked it up. It has a pH of around 6.6-6.8, is pink in color, and does have an electrical charge in it that kills the mites and explodes the eggs. Go to Youtube and watch some of the videos of it working. IT'S THE SAFEST THING TO USE ON FLOWERING PLANTS TO KILL MITES.
Now, if you are looking for something in the acid/alcohol category, try Liquid Ladybug. It has the following ingredients in it:
Peppermint oil 2%
Geraniol 1.5%
Citric Acid .5%
This has a very low pH, I think around 4.4. There are a number of other similar products on the market advertised under different names. These types do their thing and then evaporate off the plants rather quickly, no need to rinse them down. Apply only with no wind or fans on for best results.
Both products work by coming in direct contact with the mites and eggs. I've used numerous gallons of both and Mighty Wash works better. There's always going to be haters and non-believers........to each their own. I was a non-believer for a long time.......I'm not anymore.