According to the Leased Equipment section of the Residential Customer Agreement you only have to pay for repairs if you break it.
"B. You shall notify us promptly of any defect in, damage to, or accident involving the equipment. All maintenance and repair of the equipment shall be performed by us or our designees. DISH Network may charge you for any repairs that are necessitated by any damage to, or misuse of, the Equipment."
If my 522 dies because of a defect in the equipment (say the hard drive fails) I expect Dish to repair/replace it for free.
I agree, it doesn't make sense that I should be expected to pay extra for a warranty on equipment I don't own.