It's obviously a personal preference. I happen to use poles to lessen the load on my knees and back on trails with steep bits. If you're like me and have back issues, chances are that a single stick won't be of much use since your shoulders/back will likely be out of alignment the whole time you're using it. If you're intending to get the added benefit of using your upper body to propel you up a hill, a stick probably isn't for you, either.
However, if you happen to be accosted by a band of merry men, a good piece of hickory can scarcely be beat. Sure, poles will hurt, but aren't likely to render anyone unconscious. A walking stick has sufficed for thousands of people for millennia, so clearly they're effective for those who choose to use them. And there's no doubt that you can find the same price range for walking sticks as you can poles.
If you don't hike frequently, buy a cheap set of poles. If you do, and you use them, you'll see the difference in value/price within a season or so. I wouldn't choose to lean against anything that's only worth $10, but then I might be afraid to lean on something that cost over $100. Borrow a set of poles and a stick from a buddy or two and see which works best for you before you sever a digit or part with wasted money.