Unless you've got some sort of deficiency in your diet or overriding medical condition, your body isn't going to even absorb most of that multivitamin. The results you feel are largely the placebo effect.

That being said, there are certainly plenty of more expensive things people blow their money on because they think it helps them. Plastic surgery, TV preachers, and the promises of politicians to name just a few. So rock on with your pill popping self!