https://backpack.tf/classifieds?item=Balloonicorpse&quality=11&tradable=1&craftable=1&australium=-1&killstreak_tier=0

Buy orders start at 4.29, ~4.3 keys.

No currently existing sell orders.

Bot.tf Sales:

https://ibb.co/myMbPpg

https://ibb.co/CsGx46S

1 Sold for 7.86, ~7.85 keys.

1 Sold for 4.09, ~4.1 keys.

Marketplace.tf Sale:

https://ibb.co/BCvQz3v

1 Sold for $35.00/ 1.88 = 18.61, ~18.6 keys.

SCM Sales:

https://ibb.co/ct0KwZz

1 Sold for $9.48/2.33 = 4.06, ~4.05 keys.

1 Sold for $10.35/ 2.32 = 4.46, ~4.45 keys.

1 Sold for $10.01/ 2.23 = 4.48, ~4.5 keys.

1 Sold for $17.25/ 2.32 = 7.43, ~7.45 keys.

1 Sold for $16.09/ 2.34 = 6.93, ~6.95 keys.

1 Sold for $14.90/ 2.34 = 6.36, ~6.35 keys.

1 Sold for $12.45/ 2.27 = 5.48, ~5.5 keys.

1 Sold for $12.62/ 2.31 = 5.45 keys.

1 Sold for $12.90/ 2.35 = 5.48, ~5.5 keys.

1 Sold for $10.08/ 2.30 = 4.38, ~4.4 keys.

1 Sold for $11.46/ 2.36 = 4.85 keys.

Excluding all other sales due to them being too low for current buy orders. Based off judgment without a clear limit to how high the limit can be, I'll be using the most common sale value ranges as the overall range, meaning those sold for 6.95 keys or more will have to be excluded. Going with 4.4 - 6.35 keys.