https://i.imgur.com/beuArMh.png

^ Non-accepted incoming trade offer at 0.88 ref for 8 Aqua Summer 2013 Coolers (0.11 ref for each cooler).

https://steamcommunity.com/market/listings/440/Aqua%20Summer%202013%20Cooler%20Series%20%2366

^ Recent sales at ~0.44 ref and ~0.64 ref (if 1 ref = $0.065).

https://marketplace.tf/items/5650;6;c66

^ Recent sales at ~0.74 ref (if 1 ref = $0.07).

https://i.imgur.com/NHKRDX3.png / https://backpack.tf/item/1943332107

^ Sold for 1 ref.

Not counting the incoming trade offer as it wasn’t accepted.

Not counting the 1 ref sale as it is out of the ordinary.

Going with 0.44 ref due to the Steam Community Market sales and 0.77 ref due to the Steam Community Market and Marketplace.tf sales.

0.74 ref is automatically rounded to 0.77 ref.