Cost per gram of active
A bottle price tells you what a serving of a compound form costs. What you're buying is the elemental or active fraction — and that ranges from over 85% (creatine monohydrate) down to 7% (magnesium threonate). This converts label numbers into the one that matters. Two magnesium products are preloaded: the cheaper bottle loses.
€1.66/gof active · 16% of labeled dose (magnesium citrate) · 60 mg active/serving
€0.36/gof active · 60% of labeled dose (magnesium oxide) · 300 mg active/serving← BEST VALUE
The cheapest bottle here is not the cheapest per gram of active compound — once you count only the elemental/active fraction, the price order flips. That's the whole point of this tool.