Potassium has a recommended daily intake of around 3500-4500 mg. The largest pill supplement I've seen is 600 mg. Most are in the 200-300 mg range. 99 mg in the US A banana is 300-400 mg of potassium in comparison.
Meanwhile you can go to the grocery store and buy "low sodium salt" by the kilogram where half the NaCl is replaced by KCl.
Given that I can go to Walgreens and get homeopathic stuff that's a few orders of magnitude further in the opposite direction...
Not uncommon, I think. You can also grab a random multivitamin off the shelf and you regularly find stuff in there at 5-100x daily recommended doses (though those are generally things safe for significantly higher doses for extended periods, e.g. vitamin c)
I wonder how common this is in pharmacology.