With vitamins and minerals the problem sits in the unit on the front. A 500 milligram capsule of magnesium bisglycinate does not contain 500 milligrams of magnesium. The difference is more than a factor of seven.
Below is what a daily dose costs per product, set against the EU reference intake. For minerals there is a step before that: the elemental content. Only that part is the mineral itself; the rest is the salt form or the carrier around it.
For magnesium the breakdown per form is on its own page.
