1. Brand: Genuine Audi parts will typically be more expensive compared to aftermarket options.
2. Quality: Higher quality tail lights may come with a higher price tag due to better materials, durability, and performance.
3. Design: Tail lights with intricate designs or special features may cost more than standard options.
4. Technology: Tail lights with advanced technology such as LED lighting may be more expensive.
5. Market: Prices can vary depending on the region or country where you’re purchasing the parts.

As a rough estimate, aftermarket tail lights for an Audi A6 might range from relatively inexpensive options starting at around $100 to more premium options that can cost several hundred dollars or more per set. Genuine Audi tail lights would likely be at the higher end of this spectrum.

Ultimately, whether a particular set of tail lights is considered cheap or expensive is subjective and depends on your budget, preferences, and priorities in terms of quality and features. It’s essential to research and compare prices from different sources to find the best option that fits your needs.