Most natural substances are sufficiently absorbed the regular oral way the way nature intended it: providing daily supplies. Only if that route isn't working sufficiently, would the ridiculous higher prices be justified. Like real deficiencies where body-stores are replenished effectively and faster. But then one still can't expect miracles with even a couple of expensive drips.
To approach in a more targeted way, one first should know one's blood-chemistry over a period of time very well - the deficiencies and excesses as well - for not making things even worse.
In my own case finally found a GP who gave me IVs (charged insurance for administration) against my Mg-deficiency and severe muscle cramps. Only the Mg-ampoules paid for out of my own pocket (€ 17,- for 5 ampoules/IVs). During my vacation to India took my Mg-ampoules with me and found a doc charging in total IRS 300,- for administration of one IV, = € 3.75.
However, it took 6 almost monthly Mg-sulfate IVs just to stop the muscle-cramps. And after in total 22 IVs I'm still only half-way, in my deficient blood-levels back to normal. So in total I probably need at least 40 IVs, with such costly drip-services costing about $4000,- just to prevent earlier mortality of Mg-deficiency, before even starting to think of increasing anti-aging.