Earlier quoted context omitted.
A truly free market has a price for contract killings--including, for instance, the current CEO of Bank of America, or the current chairman of the Fed, or someone like Bernie Madoff. If the wealthy make a figurative "killing" abusing the poor, the poor turn around and make a literal killing. An unethical executive would have to hole up in a fortified compound and surround it with hired guns, just like a Mexican drug…
Even if we assume the extreme, almost cartoonish version of free market, in which every possible transaction is legal, that still doesn't mean the action itself has to be. So you could have a market for contract killings - but you'd still be imprisoned for actually killing.
If you hire the Morag Tong to murder your business rival--who has no friends or partners ready to avenge his untimely death--who will be the one to hire Sam and Max to play freelance police long enough to bring you to justice?