The average Mercaptopurine cash price is about $45.85 for a supply of: Tablet 50 MG 30 pcs. Get our free Mercaptopurine coupon and be eligible to receive a discount. You can reduce your Mercaptopurine cost by up to 75% with our free Mercaptopurine discount card. Bring it to a participating pharmacy near you to save on your prescription medication.Mercaptopurine is a cancer medication that interferes with the growth and spread of cancer cells in the body. Mercaptopurine is used to treat certain types of leukemia. Mercaptopurine is sometimes given with other cancer medications. Mercaptopurine may also be used for purposes not listed in this medication guide.