Is it +EV to reraise an obvious cb with air?

[DJ Sensei]

Lets say the pot has 2x chips in it, villain bets x chips (your obvious c-bet at work). to raise the pot, you must call x and raise 4x more. Betting 5x chips to win 3x. so, you need to win the pot more than 5 times for every 3 times you lose it to be +EV. Seems a bit close for my taste, unless my read is dead on.

Now, if we were to instead raise to 3x, we only have to win the pot slightly more than half the time for +EV. This, however, gives your opponent 3-1 odds to call, which he likely will with overcards or any draw... so it'll be much less effective.

In any case, this is a fancy move to pull, often risking lots of chips to win a smallish pot. I'll only pull it in cash games every once in a while, with a good read. (However, I do it a lot more often in tournaments, as my folding equity is generally a lot stronger)