First, value is relative. To my grand mother, Vim has no value. Second, it is true that the price in an efficient market tends to approach the value most consumers will get out of the product (see http://en.wikipedia.org/wiki/Supply_and_demand). That being said, the value a consumer assigns to a product is always superior to the actual price he is paying, otherwise, why would he bother with the transaction at all? Hence the consumer surplus.

To come back to the original topic at hand, I believe many Vim users value Vim at well over 100 euros. Worth usually refers to value rather than price and this why I believe some people down voted you although you were technically right that Vim's price is 0. Water is not worthless although it is free, etc.

I'm not an economist but that's how I understand it.