If by "cheap ones" you're referring to the crappy foam or wax earplugs that are available in drug stores, then yes, it makes a huge difference. Those earplugs are designed to block out as much sound as possible. The problem is, they block out a lot more high-frequency sound than low-frequency sound. That's great for a noisy construction site or something, since excessive high-frequency sound does more damage to your ears than excessive low-frequency sound... but at a concert, the result of these cheap earplugs is that a lot of the higher-pitched sounds, like lead guitars, get too muted, and you wind up hearing a muddy mix of mostly low-end frequencies. On the other hand earplugs made specifically for music, such as the Etymotics earplugs many have mentioned here, are designed to reduce the sound level more evenly across the frequency spectrum, so you get a much more even reduction in overall volume, as opposed to having too much of the high-frequencies blocked out. The bottom line is, foam earplugs will ruin a concert, to the point where it's hardly even worth going. Definitely get a pair of earplugs designed for music. Keep in mind, it won't be 100% pristine sound as if you were wearing no earplugs at all... but it still sounds good, and will greatly reduce the chances of long-term hearing loss, which is cumulative (i.e., your hearing gets damaged a little more every time you are exposed to extremely loud sound). Seems like a reasonable tradeoff to me.