If you have a working bike that you enjoy, then you do not need to buy a bike now. Remember, second or third bicycles are non-necessity luxury items, for your entertainment and enjoyment. Paying a premium for this isn't all bad, but I wouldn't do it.
If you do not have a working bike, and you would like one for exercise or utility purposes, then go ahead and buy. Sure, prices are up 10-20% in the used market. But that's how the market works. If the time is now, then the price is what it is.
As another poster said, find a good working bike at a fair price, and go and enjoy it.