There's a qualitative difference between Java and say Django in how easy that is, though. With Django you can write a couple lines of code and
immediately see your results on the screen. Instead of having to figure out how things should work from the user's perspective, you can just try them out and see if they
do work from a user's perspective. Often the results are pretty surprising, and suggest new ways that you can make things even better. It's hard to do this when your edit-compile-run cycle consists of "Write new class. Change some lines to include it. Rebuild JAR file. Redeploy. Restart servers."
The advantage of dynamic languages isn't that you get your coding done 5x faster, because most projects don't actually spend all that much time coding. It's that you can do 5x as many iterations in the same amount of time, which changes the way you approach your interaction design.