It's outside the parameters of this question, but last year, I did:

PHL-IAH-EWR-CLT-EWR-HNL-SFO-PHX-HNL-EWR-CLT-IAD-SFO-PHL, 25,642 EQM for $530. That took four days.

Also, as I used to live in ANC, I have done plenty of trips approaching 11,000 EQM for a little over $300--anything routed to the east coast via LAX would hit close to the 10K mark (I think in 2010, I did five ANC-DCA trips via LAX, eking out 11K by always doing ANC-PDX-SEA-LAX-DCA and reverse). While living there, I also did two sort of mega-mileage-runs with a friend on an Alaska Airlines Visa companion certificate--the best of which was ANC-SEA-LAX-DCA-SEA-PDX-KOA-SEA-MIA-SEA-PDX-ANC, 20,327 EQM for ~$600 (with the companion certificate). I think we did it in three days, including an overnight in DC and about 18 hours in Hawaii.

If I exclude Alaska and Hawaii, it's much less exciting. I think probably PHL-IAH-SFO-SAN-SFO-IAH-PHL is up near the top (6,813 EQM for ~$150), and I can't recall anything much better than that.