Am I getting so old where I'm asking myself these things? Lol

I went to the store today to get some Vitamin D pills. I'm pretty much a vampire with pale skin so I have to supplement. The sun isn't kind to me. First, there are like 300 choices from all different brands, and then for the same product the price per supply varies so much.

Some were like a 4 month supply for $25 - $40, and then the one I got was a year supply for $17.50. Mine was the store brand, but Vitamin D is Vitamin D.

I know name brands cost more just because of the marketing, but is there anything other than the name brand that causes them to charge more when it's the same product? Do they take away or add some minute ingredient that makes them incur more cost?

I tried ordering some online because it was cheaper (about $12 WITH shipping), but the dosage I needed (2,000 IU - which is pretty standard) on some websites wouldn't ship to NY for some reason having to do with an ingredient (I tried like 4 different brands on a website)......which is really shady and I don't want that in my body anyway. So I figured I would go to some stores near me thinking I could find a deal somewhere. Nope lol