The most expensive purple wormwood is typically Artemisia ludoviciana, also known as Ludovic's wormwood. This species is highly valued for its medicinal properties and is often used in traditional Chinese medicine. The rarity and specific cultivation requirements contribute to its higher price compared to other purple wormwood varieties.

Artemisia ludoviciana is more expensive due to several factors. Firstly, it is native to specific regions in China, making it difficult to cultivate on a large scale. The limited availability of this species drives up its price. Secondly, the extraction process for its active compounds is complex and requires specialized knowledge, further increasing the cost. According to a report by the American Botanical Council, the price of Artemisia ludoviciana extracts can be up to 10 times higher than other Artemisia species due to these factors. Additionally, the demand for this herb in the global market, particularly in the pharmaceutical and cosmetic industries, has also contributed to its higher price.