An appointment at the Apple Genius Bar is free, but repair costs are dependent on the specific problem. Apple provides the Genius Bar for consumers an outlet to diagnose issues with Apple products they are unable to fix on their own.
It is recommended to make an appointment ahead of going to the Genius Bar located in an Apple store due to its overwhelming popularity. The Genius Bar only looks at issues specifically related to Apple products, so it may refuse to look at external software issues. Many Apple products come with a one-year warranty, so if the issue is covered under this, the fix and consultation could be entirely free to the consumer.