So why the %$#@& won't the FAA let someone build a modern, inexpensive
"transponder" that we could install for under $500 (perhaps even
less)??

Why must all equipment meet the highest standards??

Why is it that a "certificated" version of FLARM would likely cost
several thousand dollars and likely not be available for many years?

Think about it:

FLARM exists now and is portable. It may take some work on the
software and perhaps transmitter for it to work with closing speeds of
500+ knots, such as two jets on a head on course or glider above 10K
head on to fast jet, etc...

But, if some mandate came along to use these "as is" and every
aircraft in the US must carry one, the sheer volume would reduce the
price to just a few hundred dollars.

It wouldn't be perfect, but would likely eliminate several fatalities
a year, and many more near misses.

Granted, it wouldn't be PERFECT, but it would be MUCH better than what
we have now. Unfortunately, at least 2 problems exist:

FAA: If it's not PERFECT, we don't want it

Lawyers: It's not perfect, you knew it, and you sold it. My client's
life was saved a dozen times over the last few years, but that's not
important because last time there was a problem. So I want this
"defective" system shut down immediately and lots of $$$ as well.

---sigh.