According to the sources provided, Lipitor is a brand-name drug that contains the active ingredient atorvastatin calcium [1]. Walmart, a popular retail chain, offers a program called the "$4 Prescription Program" that provides generic medications at a discounted price [2]. In 2011, Walmart announced that it would offer a generic version of Lipitor, atorvastatin calcium tablets, for a lower price in its stores [3].

It is unclear from the sources provided whether Lipitor itself is cheaper at Walmart compared to other pharmacies. However, since Walmart offers a generic version of atorvastatin calcium, it is likely that this medication is cheaper at Walmart compared to the brand-name Lipitor. The exact price of atorvastatin calcium tablets at Walmart may vary depending on location and other factors.

In conclusion, while it is unclear whether Lipitor itself is cheaper at Walmart compared to other pharmacies, Walmart does offer a generic version of atorvastatin calcium tablets for a discounted price through its $4 Prescription Program [2][3].

Sources:
[1] https://www.drugpatentwatch.com/p/tradename/LIPITOR
[2] https://www.walmart.com/cp/4-prescriptions/1078664
[3] https://corporate.walmart.com/newsroom/2011/11/30/walmart-announces-generic-lipitor-atorvastatin-calcium-tablets-available-in-stores-today