These are not typos. Costco is selling a one-month supply of generic Arimidex for $27, while everyone else in town is selling it for over $300.
Because Costco’s pricing policy is that they charge their customers the wholesale price plus a 14-15% mark-up. (And remember: you don’t need to be a Costco member to use the pharmacy.) The other pharmacies typically try to get as high a profit margin as they can when new generics are released, presumably because they know customers are used to paying an even higher fee for the branded medicine (e.g. non-generic Arimidex retailed for more than $400).
But come on. How can you justify extracting a profit margin of over 1000% from breast cancer patients? That’s just unseemly.