Let's do this. (I'm bad at intros.)

Sale 1: http://backpack.tf/profiles/76561198056793444#!/compare/1471910400/1471996800

Sold for Death at dusk desert marauder + cloud 9 tyrolean. (the keys were not involved)

Confirmed here: http://www.tf2outpost.com/trade/28379999

The marauder is in-date, not the tyrolean. However, it is super safe to assume the tyrolean is worth more than 15 keys, which is all that is needed to cap at Arcana's buyout (75).

We have our sale 1 at 75 keys.

Sale 2: http://backpack.tf/profiles/76561198077553062#!/compare/1472083200/1472169600

Sold for 52 keys.

Confirmed here: http://www.tf2outpost.com/trade/28444576

The hat went in a few days, the intent of the seller was to quicksell, and as you will see, the value is a low outlier compared to the three other sales -> not using.

Sale 3: http://backpack.tf/profiles/76561198111608504#!/compare/1472428800/1472601600

Sold for Blizzardy Storm Reggae, Phosphorous Lucky Shot, and a strange pro KS rocket launcher. Keys not involved.

All hats are outdated. Concerning the rocket laucher, considering its tier (hypno-beam), 10 keys is the way to go, to be safe: http://backpack.tf/classifieds?item=Rocket%20Launcher&quality=11&tradable=1&craftable=1&australium=-1&killstreak_tier=3

Mini for the reggae: http://backpack.tf/profiles/76561198232041512#!/compare/1472601600/1472688000

Traded along a clean smoking fuka (taking 15) for a heart pith helmet (38).

Reggae = 23.

Mini for the phosphorous: Sold for Amaranthine Sola Topi + aussie knife.

Easily capping at my buyout of 40 http://www.tf2outpost.com/trade/28420680#latest

Lucky shot = 40

Thus, this all caps to the buyout (70): http://www.tf2outpost.com/trade/28455204

We have our sale 3 at 70 keys.

Sale 4: http://backpack.tf/profiles/76561198118496274#!/compare/1472601600/1472688000

Sold for abduction translator (60) + Strange Factory New Pink Elephant.

The pink elephant is not easy to price. http://steamcommunity.com/market/listings/440/Strange%20Pink%20Elephant%20Stickybomb%20Launcher%20%28Factory%20New%29

Some sales are very low, some seem high. But it appears it should be higher than 11 keys, the amount necessary to cap at the buyout:

http://www.tf2outpost.com/trade/28457315

We have our last sale at 71 keys, definetely supporting the range.

70-75 sounds solid. Enjoyed doing this, feedbacks welcome!