Keep in mind that not all vitamins are created equal and that sometimes you get what you pay for. I'm leery of the super cheap ones. I don't know anything about GNC's quality, but I do know their sales people are on commission and told to push certain things. I don't shop their for this reason, but if their quality is good it may be worth it for you.
I take the following:
Super Nutrition One-A-Day prenatal (we're trying
) approx $12 for a month
Whole Foods Vitamin D approx $8 a month (DH and I share this)
Vitamin B Complex subligual (can't remember brand--share this too) approx $7 month
Costco brand Fish Oil (EWG tested it and it's mercury free) under $10 for two months
The reason I take the B complex on top of a multi is that in regular pill form the B vitamins don't digest well and I take my multi at lunch (because it can interfere with my thyroid meds), so it's nice to have the boost in the morning that the B complex gives. It's better then coffee!
So I spend about $22 per month on supplements.