Those that sell their ethics turn out to be the Enron-type people in our society. They look great from the outside, everything they do seems perfect and then one day everything is revealed. People who sell their ethics get caught sooner or later and then loose all credibility.
I think lying and deceiving can be an addicting habbit. Most people who sell their ethics probably start out selling for a very cheap price and then down the road they get caught when they start to sell for higher prices, when more is at stake.
I would never sell my ethics it isn't worth it, there isn't any price I would sell my ethics for.