We're talking an expense of somewhere around 1k total over a period of a few months. While not within everyone's reach (and if a single check is performed say yearly after initial alteration of your diet also an ongoing expense), it's far from an insurmountable cost. Especially considering this directly impacts your day-to-day well-being.

If shouldered by the individual, an extra $1k over a few months, plus however much it costs to keep re-testing, and the cost of supplements or better food to correct the deficiency, is a staggeringly insurmountable cost for the people who need it most—the poor.

As you say, this directly impacts day-to-day wellbeing. It's exactly the kind of thing that should, if it's even moderately effective, be provided free of charge for every human being.

I agree with you, but I must also admit it's not much of a concern if you live in a country with solid health insurance.

I had a load of blood tests done in the uk and the health insurance company were charged over £1000. I couldn’t believe it!

Define "a lot"

I remember doing some tests once that had a cost breakdown and they would vary a lot in price (meaning some would be let's say, single digits, some others would be in the triple digits area - think USD/EUR price ranges)