The 2.6 sale is an outlier in my opinion since there is a 2.5 seller (http://www.tf2outpost.com/trade/23232755) and the B/O of the seller himself was also 2.5. Previous B/O's were also lower than 2.5-2.6.

I also dont think offers are good counterproof since people can easily tell their friends to leave some fake offers on my unusual trade to make look like they got good offers. I'll leave the suggestion open for now and see what the mods think. Feel free to countersuggest if you want.