$100 or so. such a vital tool. I couldn't imagine commercially growing without one. I used to use a more expensive more traditional microscope but misplaced it at one of my farms so grabbed one of these in a pinch. Having the screen like that is so fucking nice vs the normal eye pieces.
You can so quickly rule out (or confirm) literally every single pest in a manner of minutes. Then once a week religiously, from day one after transplanting from trays, take leaf samples from random palnts from each area of the grow and do a quick 10 second scan for bugs. So easy, so important. dope needs to be grown with preventative measures and not waiting till theres an issue and trying to fix it.