It's both a token cost and a performance cost; there's only so much that documentation can do, compared to a ton of RL on top of millions of lines of examples. The space is a continuum, but the more you stray from the trained path the higher the cost you pay.

> the more you stray from the trained path the higher the cost you pay.

Note the LLMs are trained on language semantics far beyond the mainstream ones, so language design can become quite exotic without straying too much from the training. You really do have to measure these things, I don’t see how you can make a confident assertion without data.