Q: Why would someone charge me $600.00 to replace battery cable-positive side?

Hello - on some vehicles, the positive battery cable is quite long, going from the starter to the rear passenger seat or trunk area - literally 15’ long. Besides costing quite a bit for the part, the labor to install these can be quite significant in such cases. When you say "reception", do you mean radio reception? The radio antenna can be in the rear windshield, although why this is affected by the positive battery cable is unclear. I would press for more of an explanation regarding exactly what needs to be repaired and why. For a trusted 2nd opinion, I recommend an electrical inspection performed by a mobile, professional mechanic, such as one from YourMechanic, who will come to your location, diagnose this problem, and give you an accurate assessment of damage and cost estimate for repairs.