My initial thought was that the woman and her son(?) were making extra cash by selling from a second source. But, the episode didn't go in that direction.
It's hard to believe Gus is intentionally selling an inferior product simply to make money. And putting it on the street hoping that Lalo Salamanca will find out about, investigate, and then be told a story to cover for Mike and the German engineers is a bit too elaborate. Granted, it was Nacho who told Lalo.
Nacho is secretly working for Gus though. He was definitely in on it.
Gus is building his own lab to make his own product and doesn't want the rest of the cartel finding out. Ziegler was the head of the construction team. When he escaped Lalo found out about him so Gus had to came up with something to pull the wool over his eyes and explain who this German was.
It now makes more sense why Gus wanted Ziegler dead other than the fact he escaped. I think Mike is coming to the realization that he killed an innocent man for Gus's ploy. That's why he was pissed off at the end.
