<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Originally posted by Empress:
$600 would be very tempting... that's more than the cost of my whole SIN ticket. 
Do they usually start at a certain $ [such as $300] and gradually increase it?
If/when they offer that much, you'll see me fighting with myself whether I should take the original flights and stay in C or take the bump and get the $600 and fly in Y.
Hmmm.... </font>
Generally they'll start at $200 and go up in my experience. But given that this plane was extremely oversold, and anyone who was bumped was looking at a 6 hour delay and a re-route through Portland, they started out at $600 right away.
My ticket was also less than $600 and I was flying coach already, so it was really a no-brainer for me. One thing to be aware of is that there is no E+ on SEA-NRT, if you decide to take the bump, you'll probably be stuck in a tight seat (unless you can somehow score row 30 aisle or window).
Are you upgraded on the return? If not, I would definitely take the bump, and try using the SWU for the trip back instead (which will include a night flight). The SEA-NRT you would likely be bumped to is a day time flight, so most people don't usually try to sleep much on this flight, and it does have in-seat video in coach.
Good luck!