I've never, ever, had a quality scope fail me. I've had iron sights fail on several occasions. And you can get a quality scope for around $200. No need to pay over $350-$400 unless you just want to. But there aren't many with a list price much under $200 I'd suggest.
If you choose the scope wisely they do everything better anyway. A variable scope with 1X or 2X on the low end is faster to get on target with up close and more magnification aids with longer range precision. They are a huge help in low light where most shots are taken during hunting season.
It would cost around $150 or so to get some cheaper irons added. Better sights would cost more. Just put that money toward a better quality scope