You'll need more proof of sellers than that. And an offer doesn't count :c

UNSOLD AT 8 KEYS

http://www.tf2outpost.com/trade/21394973 - 3 days unsold at 8 keys

http://www.tf2outpost.com/trade/20694885 - 4 weeks unsold at 8 keys

http://www.tf2outpost.com/trade/21182387 - 1 week unsold at 8 keys

http://www.tf2outpost.com/trade/21469331 - 13 hours unsold at 8 keys

http://www.tf2outpost.com/trade/21415403 - 2 days Unsold at 8 keys

http://www.tf2outpost.com/trade/20915620 - 3 weeks Unsold at 8 keys

http://www.tf2outpost.com/trade/21477325 - 3 hours unsold at 8 keys

http://www.tf2outpost.com/trade/21416824 - 2 days unsold at 8 keys

http://www.tf2outpost.com/trade/21407677 - 2 days unsold at 8 keys

http://www.tf2outpost.com/trade/21455700 - 1 day unsold at 8 keys

http://www.tf2outpost.com/trade/21350115 - 5 days unsold at 8 keys

http://www.tf2outpost.com/trade/21254183 - 1 week unsold at 8 keys

http://www.tf2outpost.com/trade/21336790 - 5 days unsold at 8 keys

http://www.tf2outpost.com/trade/20735179 - 3 weeks unsold at 8 keys

http://www.tf2outpost.com/trade/21318193 - 6 days unsold at 8 keys

http://www.tf2outpost.com/trade/19506836 - 2 months unsold at 8 keys

http://www.tf2outpost.com/trade/21279484 - 1 week unsold at 8 keys

Sellers

http://www.tf2outpost.com/trade/21474396 - 7 keys 7 ref

http://www.tf2outpost.com/trade/21472236 - 7 keys 7 ref

http://www.tf2outpost.com/trade/21260447 - 7 keys

You should probably do more research next time you suggest

You only have one piece of proof to support your low end...

http://www.tf2outpost.com/trade/20974212 Sold on the 9th

http://www.tf2outpost.com/trade/21442972 Sold almost immediately

http://www.tf2outpost.com/trade/21260447 Really poorly bumped and reduced from 8 keys recently

Going to downvote.

Sold mine for 8 keys within a day

http://puu.sh/areuf/dda05c6f9b.png

http://www.tf2outpost.com/trade/21495020

So, I have a strange PDA,I have gotten offers of a Bud for it and a few keys back. If anything they are going up not down. Just because people are not buying them right now does not mean the value drops. Imagine if there was 1,000 made exactly, and 1,000 people really liked engineer as a class. So about 500 of the people who dislike engy sell it, and 500 keep it. So when all 500 are sold, then 1,000 Are owned by engineer lovers who do not wish to sell. Just because someone does not want to sell does not mean its worth less either. If anything you would be lucky to find anyone selling it unless it was some kinda mix offer for an unusual.

To be honest, anything below 8 seems like a quicksell. That said, with all the unsolds at 8 I'm not sure that this range is that inaccurate.