It would require 200,000 five-cent apples to make $10,000, not just 20,000 --- 20,000 times $0.05 is only a tenth as much, or a thousand dollars.
It would probably not be nearly so simple as the FBI guy states about "if Mork bought a baby, he would not be in trouble". Yes, if Mork **unknowingly** was receiving a stolen baby (which of course was most definitely the case --- Mork had no idea that the baby was stolen), that would indeed be one thing, but the authorities would have needed to carefully investigate to determine how much Mork knew before deciding if he was subject to prosecution. Also, Mork might still be on the hook for buying a baby, since that is illegal in any case. Again, though, since Mork's intentions had been innocent and he had been unaware of this law, the FBI might be willing to "let that slide", especially since they were getting total cooperation from both Mork and his friends, and they almost immediately got the baby back unharmed.