Alternator?
 

How often do alternators go out and how much is it to replace?

Last night I was on my way home from dinner and my battery charging system light came on, then my abs light came on, then my stereo and head light shut off. I had to pull off the freeway since it was dark out and leave my car parked overnight there.

Does this sound like a typical failing/failed alternator?

... Oh and even though all electronics in the car didn't work anymore(stereo, ac/heater, all the display actually turned off.) my emergency flasher still worked! good job thinking about the little details. it safely enabled me to get off the freeway without getting hit since my lights shut off too.

How long was the light on before you started having system shut down. A charged battery should run you for a while. Might not be alternator.

If the alternator was running efficiently i should have never lost any electrical power which is why i think it's the alternator. matter of fact, you should be able to remove the battery from a running car and it should still run if the alternator is good.

Never do this to a modern car.

Not always, you should have shut off the stereo at the first sign of trouble to reduce the pull on the battery and save power for the crucial headlights. If the battery itself is dying, it could cause the scenario you experienced but of course it could be the alternator as well.

How is your key in the ignition switch? Does it turn OK and do you hear a clunk noise when you pull the key out? There is a possibility that the ignition switch failed.
Like wvboxst3r said, you should have been able to drive for a ways just on the battery alone, even if the alternator failed.

charge the battery, start the car. Measure the voltage across the terminals. If its 13+v the alternator is good.

Alternator
 

Same thing happened to my friends car and it was the alternator, if you can take it off have it checked at any autoparts store (its free) they'll do a 3 stage test on it, before you take it to the autoparts store check the voltage while on Idle it should read 14.7 volts or closer to that, btw how many miles is the car and how old is the battery too? :cool: