I am not looking back, I am looking forward. If it only costs $10/flight, shouldn't it be mandatory? Air France 447 happened 5 years ago.

http://en.wikipedia.org/wiki/Air_France_Flight_447

So, we're talking about more than once per decade.

It only took a couple of days to find where the Air France 447 crashed despite its location. Moreover, I doubt either accident would have been prevented or people would have been rescued if the precise location of the crash was known sooner.

There is some value in knowing early where an accident occurred, but that is rarely a problem. How much is it worth to fix it for the few cases that happen in the middle of nowhere?

Your statement is inaccurate:

"While Brazilian Navy authorities were able to remove the first major wreckage and two bodies from the sea within five days of the accident, initial investigation was hampered because the aircraft's black boxes were not recovered from the ocean floor until May 2011, nearly two years later"

If they knew where the plane went down, it wouldn't have taken 2 years to find the flight data recorders. The "pingers" on the recorders lasted for about 30 days, which should be plenty of time, if you know where to look.

The cost of rescue & recovery is substantial. That money could be preemptively used to subsidize the tech that affects flight safety.