It's certainly cost-effective for the defendant in the case if a principled juror saves him from years in prison. What does "cost" have to do with it anyway?
Your energy is far better spent (1) electing good judges who will hear a constitutional challenge at the proper time; (2) electing good and honest DAs who won't prosecute junk cases; (3) electing good legislators who won't pass unjust laws in the first place.
What good does a Constitutional challenge do for someone who's being threatened with 15 years in prison if he doesn't knuckle under to the prosecution's demands? What good does an election do for the victim of a junk case charging an unjust law?
Educating jurors about their rightful powers to do justice doesn't take place in a vacuum, or to the exclusion of these other efforts, in any case. I'm on the Board of Directors of my local gun rights group, as it happens.
And as you could see in those two cases I posted, a jury doing justice in spite of the law is not a "theoretical proposition" by any stretch of the imagination.
Again, the chances of a holdout juror riding in at the last minute to save a defendant purely on the theory of "jury nullification" is far fetched.
The jury is far more likely to find that the State hasn't proved its case, if the defense lawyer will just give them ONE factual basis for a reasonable doubt -- as well as present the overarching theme of his client as a good man who is being persecuted by an overzealous prosecutor.
You've about ridden your hobbyhorse to death. You can't focus on one arcane theory to the exclusion of legislative work, constitutional challenges, and good defense lawyering. The chances of succeeding through the latter three are far greater, and your victim of prosecutorial persecution had better put his trust in a good lawyer who files a constitutional challenge for him, rather than the vanishingly small chance of getting a holdout juror.
Some sort of public education/information program on jury nullification isn't going to do the guy in the hot seat right now any more good than legislative efforts or constitutional challenges. But legislative and courtroom work will keep more folks from being put in the hot seat in the first place.