DirectTV Wants to Charge $300 Dollars for Cancellation

I’ve been with DirectTV for about ten years now. An aunt of my, woke up one day to see that the DirectTV box no longer worked. Normally she called DirectTV so they can fix it, since we technically rent the box from them. When you terminate your contract, you are obligated to return the DirectTV box back to them.  Any appliance of any sort always come with a warranty, customer service said that the box was out of warranty (warranty is only for 90 days). The customer service associate told her that it would be $50 (cash only) for a technician to come to her house see what the problem was.  My gripe is this, if DirectTV owns the box, shouldn’t they just come and fix it free of charge? There is no damage of any sort to the box it just died.  Now she has threatened to cancel her service but according to the CSA, the cancellation fee is $300. Can someone tell me how any of this seems fair? I just want DirectTV to replace the DirectTV box so she can go back to watching her favorite TV shows.