SUCCESSS!! (Bad news first: I'm an idiot. But the good news is
the creak is gone!)
~replacement ceramic-bearing bottom bracket: $149.00
~replacement chainrings: $178.90
~replacement chainring bolts: $26.95
~teflon tape: $4.99
~mechanic's stethoscope: $6.99
~Etymotic noise-reducing ear phones (
to make riding tolerable): $79.00
~time spent repeatedly removing, meticulously cleaning, greasing, reinstalling parts: >6 hours
~discovering that the source of the creak was
an insufficiently-tightened rear skewer: Priceless.
There are some things money can't buy; sadly intelligence is one of them.
I already had the earphones, mech's stethoscope, teflon-tape, and chainrings, but I'm seriously high-fiving my own forehead right now.
I've paid the tuition, hopefully someone else will glean some wisdom from my foolishness. Many thanks for all the suggestions!