JK Galbraith Quote: How to interpret? I came across a very thought-provoking quote by JK Galbraith concerning supply-side economics. The quote is as follows:


  The poor don't work because they have too much money. The rich don't
  work because they don't have enough money. If you believe that, you'll
  believe anything. -- J.K. Galbraith


With famous titles like: The Affluent Society, Galbraith was a expert in economics. Also he is very witty, and between these qualities I'm having a hard time connecting the dots for myself. I'm not sure how much of his explanation/comment is sarcasm and how much is genuine.

Question: Is there any notion/assumption/principle in supply-side economics that could legitimately be alluded to in Galbraith's remark here? 

In other words, he must have phrased it this way for a reason; and let's not forget, this is in the context of supply-side economics. So by juxtaposing these false statements with our intuitive understanding of supply and demand, it's as though he's mocking that school of thought. So what is the original concept of the supply-side school of thought that he his mocking? 

Surely there is something he thought was paradoxical in supply-side theory that made him say this comment.
Here is the quote, rephrased:

This is a false statement: (A) the poor don't work because they have too much money.

This is also a false statement: (B) the rich don't work because they don't have enough money.

If you believe those false statements (A) and (B), you are very credulous.

The poor have a much higher marginal value of money than the rich, so their incentive to work, to earn more money, is very high. For the rich, it's the other way around.

Ken is making explicit two assumption that are fairly common (in that school of thought and some other Conservative groups), but rarely spoken so plainly, and rarely spoken together. When they made explict and are put together, it makes it much clearer that to hold both of them at the same time is absurd.