It's just like any industry. There are so many powder manufactures out there. Some are punting out shit test e, probably to keep up with demand, maybe the just dont care(and possibly other compounds). It's not like you cant make quality test e raws because the earths atmosphere has changed. The manufactures have been slipping, because they just don't care.(its just for stupid juice heads anyways right, you can bet they are not using their product, just in it for money)
And some take pride in offering great quality. Just depends who whatever shop gets their powder from. It's who you know, and what channels you have to get your product.
I'd bet a lot of labs use the same group of powder source. And then some who have spent a bit more time have found higher quality, higher security, more selective powder sources. But I'm willing to bet the top notch powder sources aren't responding to some bros who just up and decided to start slinging gears(say for instance if i were to take it up. Hell, i could do it, these formulas are not complicated. But it's more then that, you have to have connections. And I'm sure most powder sources on boards are not as great as they will tell you they are. There may be some gems. Of course. I've not pursued it)