Xiongmao Shaoxiang 

A virus writer in China has been arrested for developing and selling viruses. These viruses have infected millions of computers and were targeted to steal passwords for the ubiquitous QQ service, according to Xinhua.
The individual and his associates earned 100,000 Yuan (about US$13,000) selling the viruses to 120 individuals. This criminal team mutated / customized viruses for their customers.
These numbers should scare anyone who cares about the health of the Internet and computer security.
Millions of computers infected for only pennies each (assume "only" 1 million infected computers - the revenue per infection was about US$0.013 while the damage per infection was no doubt much higher).
What we don't know at the moment is how much money the buyers of these viruses made - almost certainly their return on investment was very good (I haven't seen any data on those individuals - help from China / Chinese readers?)
This is for a mass-market, non-targeted infection. To target a specific company or individual, the rate may be higher, though the total cost would likely be the same (since the work is equivalent) but the likelihood of detection would plummet.
The economics of this highly destructive form of computer crime are going to drive its popularity - and commercial virus development scales much better than the current security countermeasures.
Eight arrested in virus case
www.chinaview.cn 2007-02-13 09:13:06
The pictures shows the logo of Xiongmao Shaoxiang (Panda burns joss-sticks), a worm that has hit millions of computers in the country since November 2006.

Omg that evil Xiongmao Shaoxiang virus... so evil.

Xiongmao Shaoxiang by harrold hunt May 9, 2007