IMHO, the real savings for dynamic vs. static languages is in how it changes your thinking patterns. For instance, when confronted with a problem that involves filtering out duplicate strings, programmers for dynamic languages reflexively reach for an associated array (a hash in Perl, but not necessarily implemented with a hash algorithm in other languages). Users of static languages tend to create their own solutions, even if they have something like an associated array readily at hand (like java.util.Hash). This nearly always results in the dynamic language implementations being smaller, clearer, and more robust.

Of note, I don't think users of true strongly-typed languages have the same problems.