I dunno, Jim, it seems like your sprocket could do another 21440 miles. Compare, for instance, this sprocket from one of the trans-Africa tourers:
(http://takeonafrica.com/wp-content/uploads/2010/08/img_9413.jpg)
Only joking! That's a fascinating report, admirable in its instructional level of detail, and I agree with you wholeheartedly: you don't want to save a few bucks if it risks your life in traffic.
I've saved your sprocket pic to compare my sprocket at 10720m/17250km to check if needs turning yet. There's a difference in our riding milieu -- I have no dirt roads at all -- and transmission management -- I run my chains for their entire life solely on factory lube inside a Chainglider, zero extra lube -- but your approx 10K per side seems like a reasonable aspiration.
Thanks a lot, Jim.