Screenshots of me buying pip boys:

http://i.imgur.com/lrURJsZ.png?1 - Bought for 1.55. 3 days old

http://i.imgur.com/kTXyZIJ.png?1 - Bought for 1.55. 1 day old

http://i.imgur.com/RgdF7Kk.png?1 - Bought for 1.44. Just today

Buying for 1.66:

There were none buying for 1.66.

Buying for 1.55:

http://www.tf2outpost.com/trade/8008417 - Not currently buying

http://www.tf2outpost.com/trade/6760986 - My trade. I have plenty of success.

Other:

http://www.tf2outpost.com/trade/8069390 - Buying for 2 scrap + a spectre's spectacles. Interesting...

So in conclusion, it is definitely possible to buy these for 1.66 refined. The reason I don't have much proof is because i didn't include the buyers at 1.33 and under, and I didn't feel including the sellers was necessary. Let me know if you want me to list those as well.