Two recent sales.

Sale 1:

Sold for Mallard Glove + C9 Snaggle:

http://backpack.tf/profiles/76561198133348135?time=1446102000

http://backpack.tf/profiles/76561198133348135?time=1446188400

=46 * 0.9 =~42 Keys

The items were then offered(neither had trades) with 4 keys in items on a DBD Teutonic Toque

http://backpack.tf/profiles/76561198133348135?time=1446188400

http://backpack.tf/profiles/76561198133348135?time=1446361200

=50 - 4 =46 Keys

The toque then sold for a Scorching Nano

http://backpack.tf/profiles/76561198133348135?time=1447488000

http://backpack.tf/profiles/76561198133348135?time=1447574400

=50 Keys

The nano, according to polar, sold in 4 days for 50 pure:

http://www.tf2outpost.com/trade/27388594

=50 Keys

Sale 2:

Probably offered on and sold for Vivid Falkrik

http://backpack.tf/profiles/76561198052449359?time=1444546800

http://backpack.tf/profiles/76561198052449359?time=1444633200

Sensei had no trade, so overpay isn't applied for this sale

=43 Keys

Falkrik Mini:

http://www.tf2outpost.com/trade/27503504

http://backpack.tf/profiles/76561198151233676?time=1448870400&compare=1448956800

Sold for Screaming Tiger Buy a Life

Not applying overpay as the seller clearly wanted a tiger buy a life, but capping at B/O 43

=43

Tiger Buy a Life

http://backpack.tf/profiles/76561197962588421?time=1447056000&compare=1447228800

Sold with ~3 keys in sweets for Grail Buy a Life. Grail had no trade, probably offered too

=48 - 3 = 45 Keys

Grail Buy a Life Mini:

Sale on the grail Buy a Life:

http://i.imgur.com/n47SoGL.png 52 Pure

http://www.tf2outpost.com/trade/27128979

http://backpack.tf/profiles/76561198107678494?time=1443682800

http://backpack.tf/profiles/76561198107678494?time=1443769200

45 pure, didn't even take a week

Overpay doesn't appear to be necessary for the mini, given how easily this turns into pure.

So the grail Buy a Life is valued at 45-52 keys Pure here.

That would make the mini for the tiger buy a life 45 Keys