Alternator Replacement for a 2006 Toyota Camry Solara

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When I started my car, it had the sound of a power steering going bad; I turned it off and it started right up with the same sound. I saw no indication that my battery or anything else was wrong, until I noticed that ALL the indicators on my dash board were lit up and flashing; and I was loosing accelerator power. I got to a safe place and the indicators were still on when I put my car into park. Waited for about 5 minutes, indicators lights still on, so I turned the car off. Of course, it would not start so, I called a tow truck and had it sent to Principle Toyota, which was about a block away and this was on a Friday afternoon around 3:00 p.m. Received a call on Saturday morning stating that I needed to purchase their battery @ $168.00 before they could proceed with a diagnosis; later was told - needed an alternator; mine was only showing a 12.5 voltage @ at that time with a cost of $523.00. Is replacing an alternator for a 2006; with 79,800 miles this costly?