sale #1 - 22 keys

https://backpack.tf/profiles/76561198039912258#!/compare/1585958400/1586131200

https://backpack.tf/profiles/76561198087016902#!/compare/1586044800/1586217600

sale #2 - untrace

https://backpack.tf/profiles/76561198133684216#!/compare/1586736000/1587686400

https://backpack.tf/profiles/76561198447257724#!/compare/1586736000/1586822400

sale #3 - 17 keys

https://backpack.tf/profiles/76561198447257724#!/compare/1586908800/1587081600

https://backpack.tf/profiles/76561198829227536#!/compare/1587168000/1587254400

sale #4 - 18 keys + 20 ref

https://backpack.tf/profiles/76561198302976864#!/compare/1587254400/1587340800

https://backpack.tf/profiles/76561198829227536#!/compare/1587254400/1587340800

sale #5 - untrace

https://backpack.tf/profiles/76561198188659387#!/compare/1584576000/1584662400

https://backpack.tf/profiles/76561198142721484#!/compare/1584576000/1584662400

sale #6 - untrace

https://backpack.tf/profiles/76561198188659387#!/compare/1586044800/1587168000

https://backpack.tf/profiles/76561198305494036#!/compare/1586304000/1586390400

sale #7 - untrace

https://backpack.tf/profiles/76561198394457682#!/compare/1585612800/1585699200

https://backpack.tf/profiles/76561198070665208#!/compare/1576108800/1585699200

sale #8 - I would say the downgrades but the histories on all the items dont match

https://backpack.tf/profiles/76561198394457682#!/compare/1588636800/1588723200

https://backpack.tf/profiles/76561198100836666#!/compare/1588550400/1588723200

sale #9 - use there

https://backpack.tf/profiles/76561198100836666#!/compare/1588723200/1588809600

https://backpack.tf/profiles/76561198085142983#!/compare/1588723200/1588809600

sale #10 - scorching airdog?!

https://backpack.tf/profiles/76561198085142983#!/compare/1588723200/1588809600

https://backpack.tf/profiles/76561198312743572#!/compare/1588809600/1588896000

sale #11 - 18 keys + 20 ref in sweet

https://backpack.tf/profiles/76561198312743572#!/compare/1588896000/1588982400

https://backpack.tf/profiles/76561198153208788#!/compare/1588464000/1589068800

sale #12 - bulk

https://backpack.tf/profiles/76561198153208788#!/compare/1588464000/1589068800

https://backpack.tf/profiles/76561198268027488#!/compare/1588896000/1589068800

sale #13 - untrace

https://backpack.tf/profiles/76561198431576019#!/compare/1589155200/1589241600

https://backpack.tf/profiles/76561198268027488#!/compare/1589155200/1589241600

sale #14 - https://marketplace.tf/items/tf2/617;5;u30 | https://backpack.tf/item/613199682 | no clue on b/o

$37.78 / $1.75 = 21.59 keys

----

Taking 18 - 22 keys

excluding 17 keys and sale #10 due to being low and high respectfully.