Bigger factor I think is that 06 will be soon 9 years old car. Also 08 and up are more desirable because the premium gas is no longer recommended for them.In michigan they are pretty underpriced compared to other places. I was doing a ton of research to find the best deal and almost bought an '09 with 123k for $11,000 out the door at a dealership. I ended up yesterday just buying an '06 with 98k for $7,000 that was in mint condition from an older gentleman who only drove it to visit his family in the UP and during snow days. I think the fact though these are not being made any longer immediately drops prices.
I'm still not sold on the whole premium gas thing except maybe for long trips, I think doing city it should be pretty negligible.