Is buying before Ex-Date In a LOW TAX BRACKET free money?

Let's say my income is very low as a retiree, student, etc. To a hedge fund or rich person owning a stock, if they receive a $1 dividend it's really not worth $1 because of taxes. It's probably worth $0.70, so the stock should drop by (1- average stockholder tax rate) * dividend amount in theory, right? if it actually drops proportional to the dividend that doesn't make sense in efficient markets. I would just sell before the dividend hits and re buy at that cheaper price to not pay taxes on the