I'm sure poisoning customers is bad for business, but the stakes are as high as it gets (pun intended).

Statistically speaking I'm sure a very low percentage of people that do drugs get in trouble with law enforcement as well.

Still, it speaks volumes about the buyers' risk aversion which was the original point.

That being said you have a good point about testing. Personally I'm not a consumer so I don't know how widespread testing is.