The miner earns more than he pays for electricity, otherwise it is unprofitable to engage in mining. The miner can mine new coins that are not yet on the exchange, and due to this, earn a good profit. The price of video cards is cheap now, and will not fall much lower, so buying video cards can be a good decision if you believe in mining.
Mining makes more sense if the coins is not yet on the market and it later gets listed and price shoots up or if the mining gear is somewhat efficient. But imagine someone mining a regular coin using old-not-so-efficient GPUs that are almost obsolete. They are in most cases going to do it at a loss in a bear markets which is why if someone just bought the coins using the money, they would be better off.
But anyways mining makes someone more involved.