How much does a headlight restoration cost?

Awesome Headlights charges $60 for both headlights, and $40 for a single. This is very reasonable, considering the cost to replace them.

Do headlight restoration products really work?

If there is a small amount of oxidation, yes. However, if the oxidation or yellowing is heavy, they won't. Additional sanding products will be needed.

Is it safe to have faded, yellowed or hazy headlights?

Definitely not. Deteriorated headlights reduce the amount of light output. The beam from the headlight is weakened, and results in a reduced area or range of coverage.