I Did not know about this cottage industry.

I'm also quite surprised that "operators start as customers"

Is it because operators are script kiddies that are "renting" someone elses software, or in effect, operators are just resellers?

This assumption is based on that, if you are someone technical that can create spftware to develop a botnet in the first place, you arent likely to buy it from someone else unless its really not worth your time.

And if indeed script kiddies are resellers of anothers software , what are the costs to rent/buy the malware? And why does the FBI not go after them?