I am repairing my brothers car which quit on him because the timing belt stripped/broke. He got the car and did not change the timing belt, and the piston did kiss a valve (actually it whacks the valve quite hard). It hit all of the exhaust valves enough to bend them. The intake valves are also not good.
On this picture, the valves on the lower row are the exhaust valves, and they are all stuck open because they are bent. The one on the left is bent at a 90 degree angle.
That severely bent valve got hit by the piston on the right. It put a good dimple on the top of the piston, but it can be saved.
To fix the head, it costs around $1200 bucks because all of the exhaust valves have to be replaced, if the head is salvageable, and all of the valves have to be ground to make it even. Labor to remove and reinstall the top and front of the engine is around $750. Parts alone are $650. $2550 later, you get your car back.
If you replace the timing belt under the manufacturers recommended replacement schedule, which is every 60,000 miles, the cost is around $600.00 parts and labor.
My brothers car is a Mitsubishi Eclipse with the 4G63 2 liter engine.