Honestly, it depends. The farmers all grow their own plant material, which eventually becomes the plant at the end, so it's not like they buy in plants and just graft them. Saying that, some farmers care less about the end product than others, and while we have been sorting them (we all come together to sort them through a cooperative), you can definitely see there's differences. Then you have other factors common to everyone who grows plants such as weather and soil. Finally, the workers themselves are almost always immigrant workers who aren't paid a great deal, and it's hot hard work, so there's that. But I reckon after sorting, you'd have a plant stock that is around 99% good stock. I'd also like to say that the guy I work for is pretty meticulous, you have to work hard and pay attention but he takes care of his workers, and the end result is that he has very few bad plants that come through normally, and it's always good to know you've been a part of that!

TL:DR The plants that are grown can be of varying quality, but after the sorting process, I wouldn't worry about buying the plants here.