Bit sets can be purchased for very little and very much money. Roughly, a realistic range is between six and 100 euros, although the range upwards can actually be titled "open-ended". Refined tips are usually more expensive, of course. If you work with the bits a lot and also with hard screws, this is a good option because otherwise the bits can wear out very quickly.
If you rely on the bits often or even daily, you should look for high quality. For occasional household work, normal bits are sufficient. If they break, they can easily be replaced until the next use.