If not, why would growing crops be a cheaper solution? What is the opportunity cost of growing golden rice to feed your vitamin deficient family vs. growing something else to sell on a broader market?
On the consumer side, one can explain that the new golden rice is better and keeps your family healthier than regular rice. It's simple enough to be understood by people with low levels of education that the yellow one is better, and can easily be communicated to other members of the family who may not be able to read. There might be issues with counterfeit rice (dyed yellow instead of being actual golden rice), but that would be a separate problem.
In the cases where new behaviors are wanted, it helps to root them in culturally specific ways. For example, for iron supplementation, one way to increase the amount of iron consumed is to use a few drops of acid (such as citrus juice) combined with an iron ingot. This was done to alleviate iron deficiency in South East Asia.
Obviously, this was a very foreign behavior with low compliance, until they reshaped the ingots to be fish shaped, leading to the "lucky iron fish." Explaining to people that if they cook with the lucky fish in their pot, the fish will bring them good luck and health. This has led to much better compliance and outcomes.
[1] https://data.unicef.org/topic/nutrition/vitamin-a-deficiency...
Many of the vitamins and minerals are cheaper to produce at high quality with industrial production, such as ascorbic acid (around $12/kg - https://www.foodbusinessnews.net/articles/10836-vitamin-c-pr...). The dosage can be more precise in this way.
Also with diabetes and certain other illness, some nutrients can't be taken at a required level from natural sources due the amount of other nutrients, e.g. carbohydrates.
https://www.youtube.com/watch?v=mZ6nREONy_4
Making vitamins taste like candy increases compliance (good), but you can overdose on fat-soluble vitamins like A (bad). "Just take a pill" is not a great solution.
Also, since when do we need "compliance" with regard to offering a cheap solution to a common problem that isn't infectious? People are intelligent enough to know what they should do. Let them have the free will to take the solution or not. We don't need to force or seek "compliance". That just sounds kind of dystopian or authoritarian.
I’d rather give a dollar to the local homeless shelter and watch them burn fuel with it at night, than my cent going straight to corrupt governments and militias.