Spend almost a grand on a set of Tivoli radios and...

Spend almost a grand on a set of Tivoli radios and speakers. Realized at home that one of the audio cables was defective and they refused to exchange the cable when i went back to the store or give me a replacement, stating that i had to purchase the 20$ cable from them. How a store could sell a defective product and then ask client to purchase another one is beyond my comprehension.