The police couldn't find a record of the alleged murder victim, so I'm guessing that "redandwhite" and "friendlychemist" were the same person, just playing a con on DPR to get some cash.
I took it to mean fast and relatively painless versus protracted suffering, i.e. "non-clean", messy.
Without the 'respectively', it's ambiguous whether the clean or non-clean were the cheaper of the two alternatives.
http://en.wikipedia.org/wiki/Veronica_Guerin#Murder
Clean: Traffic accident, apparent suicide, etc.
You'd probably create more evidence trying to make it look like an accident than you'd clear up just by doing it some easier way.
That would be hazardous in my opinion. Now you have two places where you can place the preparator.