Henry's already given a good answer, but I would just like to pick up on this part of your question:
But does it not come with a performance tax?
The performance overhead of a framework is negligible.
In fact, you may even get better performance from frameworks such as ColdBox, which have built-in caching.
Remember, most frameworks are mature codebases used by lots of people - most likely, your newly written untested code is going to be the culprit, not the framework.
However, as a general rule (not specific to frameworks) performance is not a problem unless you've got measurable results that say it is.
i.e. don't just think "I'm going to do X instead of Y because I think it'll be faster" - go with the simplest option that meets user's needs, and only change it if you can prove that it has a performance problem and that your proposed solution is better.