I did the identical routing earlier this year, but instead of EWR, left from CAE. Had meetings in Redmond and got tix. THen later found out I had to be in SFO for a conference a day after my meetings in Redmond. It was cheaper and easier to arrange to come back to CAE than to change my tix for a fee and pay from SEA-SFO. Total cost for the trip was around $650, all of which was paid for. As far as a MR goes, it is pretty high for only about 9500 miles, but I didn't have to pay for it...I only had to fly it.

My only problem was that I checked a bag and wouldn't you know that waiting for my bag almost cost me my second outbound. Baggage conveyors broke and instead of 1 1/2 hours in CAE, had 25 minutes to get my bag checked again and board. Luckily the people at the ticket counter had just walked my bag from the back to luggage claim so they didn't give me a hard time about the timing (CAE is a small airport).