At the end of your handlebars there are, or should be, tiny pieces of rubber or metal to blunt the jagged metal ends of your steering mechanism. In terms of cost, you couldn’t get much cheaper. Most can be bought for a couple dollars, but as with everything biking, you can spend as much as you’d like–there are some that will set you back 50 dollars.
Not only does this little piece of rubber or metal keep water and debris from entering your handlebars, but it also could prevent the necessity for stitches and a costly emergency room visit. These caps are especially essential for road bikes, with the handlebars facing towards you. Without the plugs, an otherwise inconsequential bump into your handlebars could put a hole in your stomach.
Safety is not the time to be cheap or lazy. Go to the store and get some plugs on your bike if they aren’t already there. Save money other ways, but not on handlebar plugs.