Do Dynamic Languages Make New Code Cheaper?

Loud Thinking:

Finally, the new economics of dynamic languages like Ruby simply makes reuse a lot less attractive. Since the cost of producing new, original code is so much lower…

Hang a tick, why is new code cheaper with dynamic languages? Sure, you can write the code faster but the vast majority of cost involved in code isn’t spent up front, it’s spent in maintenance. So writing new code hurts because you don’t take advantage of all the money already spent on maintaining existing code and instead incur extra maintenance cost.  Even if the initial cost of writing new code was reduced to zero, new code would still be very expensive purely because of the maintenance element.

I might buy it that programmers are more productive using dynamic languages, I can’t see any evidence that dynamic languages have any significant impact on maintenance costs. In fact, a lot of the flexibility of dynamic languages can make it very difficult to maintain the code because it can be hard to find where the cause of the fault is.