Radio/Sound System Faults

I have a 2011 Hyundai Sonata GLS Executive with a standard factory sound system. It has an intermittent fault which is getting worse. The radio/CD/Aux sound starts getting scratchy and then stops completely. If you tap the radio face it comes back on for a while before going through the whole cycle again. Hyundai Cedar Rd tell me that the radio needs replacing at a cost of R27,000 and that it is not covered under the 150,000km warranty that Hyundai make a big thing of when they sell the car (my car has around 77,000km on it). The same radio is available on e-bay as new old stock at R5,000 and guaranteed used units sell at between R400 and R1700. I have to ask why the warranty would be selective and not cover the radio which is factory fitted? This is not a premium sound system so where does the outrageous price come from? Well, for the sake of a quick buck they have just lost a fleet owner. I will never buy another Hyundai at any price and caution anyone who is looking at one not be lulled in to a false sense of security with the warranty. Great customer retention marketing Hyundai!