Most raws are pretty good and products are usually dosed okay for the price. For painful compounds people under dose them slightly to reduce PIP. But stuff like test is simple and cheap. Aside from prop and ace which ate usually slightly under dosed, most compounds are pretty accurately dosed. Stuff like primo is another thing, but the common bread and butter compounds are relatively safe bets.
It's not really the raws and dosing that's the problem, it's sterility, oils and carriers, stuff like that. UGLs can use cheap oils and extra BA to "play it safe" and that can really bring the quality down. Not everyone sterilizes with autoclaves and dispenses products using laminar cabinets and all that fancy jazz, it's usually brewed in a room that's hopefully sterile, with vials and whatman filters purchased from whomever has the best deals online, etc. I know guys who try hard because you can make an exponentially safer and better product with minimal efforts. But when important steps are skipped the quality suffers.
I met a decent hookup and brewed test and tren in big vials for personal use and it was easy and economical. If that's not an option, try purchasing above the local guys head if you can. The higher you move up the chain the more you can know about their standards and protocols. Most guys that aren't jaded and disenchanted with bodybuilding take pride in their work and are competitive. If not, a competitor will do better and take their clients. Simple as that.