Lipitor is a brand-name medication used to lower cholesterol levels. According to [1], the drug's patent expired in 2011, and several generic versions of the drug have been introduced to the market since then. As a result, the cost of Lipitor has decreased significantly. In 2011, the cost of Lipitor was around $150 for a 30-day supply, while the cost of its generic version was around $10 for the same amount. This represents a cost difference of around 93%.

Generics are drugs that are identical to brand-name drugs in terms of active ingredients, strength, and dosage. As explained in [2], generics are usually much cheaper than brand-name drugs because they do not require the same amount of research and development costs. Additionally, the introduction of generics to the market increases competition, which can drive down prices.

In the case of Lipitor, Pfizer, the manufacturer of the brand-name drug, has aggressively marketed the drug to try to maintain its market share. According to [3], Pfizer offered discounts and incentives to patients and healthcare providers to encourage them to continue using Lipitor instead of switching to generic versions. However, despite these efforts, the cost of Lipitor has continued to decrease as more generic versions have become available.

In conclusion, the cost difference between Lipitor and its generics is significant, with the generic versions being much cheaper. This is because generics do not require the same amount of research and development costs and the increased competition drives down prices. While Pfizer has attempted to maintain its market share by offering discounts and incentives, the cost of Lipitor has continued to decrease.

Sources:
[1] https://www.drugpatentwatch.com/p/tradename/LIPITOR
[2] https://www.express-scripts.com/pharmacy/blog/generics-vs-biosimilars-what-are-they-and-how-are-they-different
[3] https://www.nytimes.com/2011/11/30/health/generic-lipitor-sets-off-an-aggressive-push-by-pfizer.html