when my friend and i would make BHO.. we would purge that shit over and over for hours w/ an electric vac pump in a polycarb vac chamber.. over kill w/ it..
i'm guessing most vendors and collectives that make their own, aren't as picky about the purge. or since time is money, they don't want to take the time out for you.. also a lot of people get good looking wax that is purged half-assed, and rave about how bomb it is.. and that lowers the bar.. unfortunately as long as there are people willing to buy that quality med, they'll happily sell it.. once more people are educated, and start having higher standards outspokenly maybe that will change.. but its about money and most people don't know(care) what they're doing or cut a lot of corners and go for looks.
like puffers said look for shatter.. its actually possible get a good idea of its purge by its looks, if you know what to look for.. wax/budder (especially in collectives) can be very deceitful. i don't mind wax/budder.. if i make it, or know what standards it was made by. a dead give away to how purged it is.. is smoothness... really purged oil is sooo smooth.. all you get is an incredible lung tingle.
PureXtracts have been good by me.. the only brand i'll even buy these days.. it's been very consistent and clean IME. but if you want something done right some times you gotta do it yourself. just don't blow yourself up!!
or Fox news might take an interest in you
*side note* the other day i saw on the local news commercial.. FOX news is doing a special on 'Marijuana Wax'.. whatever they have to say, i'm sure it'll be true and not intended to cause worry, like always