quality of ingredients, what is used in the processing, and absorption of the materiel into your bloodstream are huge factors in the quality of a vitamin. If you go pay 4 dollars for a multi, you are likely to just pass it through your bowel and not absorb it. Also, the quality of ingredients will be less, which is important when you are taking herbs, as cheaper ones have more of a likelihood of not being tested for toxins in the plant, coming from soil quality issues, etc.
There are several products on the market that are not sold in stores, but can be purchased through a chiropractor or naturopath. These are the best of the best.
A second to that would be New Chapter, found a many health food stores. That brand is life changing. It really makes a difference. I was taking something else before that, and when I switched, I literally felt my body changing after a month or two- many things in my body started functioning properly.
p.s. don't let anyone tell you you don't need a multi-vitamin, and that you can get all you need from your food. This was true 100 years ago, but today, our soil is over farmed and depleted, and everything is full of processed sugars which deplete and leech nutrients from your body while you digest them. Unless you want to become a hippie organic farmer and a hermit, you need a multivitamin.