Resuggestion, thanks to Cashew for the info!

Taking 2 months.

Sale 1:

https://backpack.tf/item/6255079516

https://backpack.tf/profiles/76561198203142530#!/compare/1589500800/1589587200

not unusual before this compare

sale 2:

https://backpack.tf/profiles/76561198203142530#!/compare/1589932800/1590105600

https://backpack.tf/profiles/76561198099141522#!/compare/1590019200/1590105600

sold for 3 keys

sale 3:

https://backpack.tf/profiles/76561198099141522#!/compare/1590105600/1590192000

https://backpack.tf/profiles/76561198969129810#!/compare/1589932800/1590192000

Bulk

sale 4:

https://backpack.tf/profiles/76561198969129810#!/compare/1590192000/1590278400

https://backpack.tf/profiles/76561198450627599#!/compare/1589673600/1590278400

Bulk / high

sale 5:

https://backpack.tf/profiles/76561198450627599#!/compare/1590278400/1590364800

https://backpack.tf/profiles/76561198280693486#!/compare/1590278400/1590364800

QS

sale 6:

https://backpack.tf/profiles/76561198080179568#!/compare/1588118400/1588204800

https://backpack.tf/profiles/76561198024454788#!/compare/1588204800/1588291200

Untrace

sale 7:

https://backpack.tf/profiles/76561198024454788#!/compare/1588291200/1588377600

https://backpack.tf/profiles/76561198216561389#!/compare/1588291200/1588377600

Bulk

sale 8:

https://backpack.tf/profiles/76561198216561389#!/compare/1588377600/1588464000

https://backpack.tf/profiles/76561199043177646#!/compare/1588377600/1588464000

QS

sale 9:

https://backpack.tf/profiles/76561199043177646#!/compare/1588464000/1588550400

https://backpack.tf/profiles/76561198164468208#!/compare/1582070400/1589155200

Untrace

sale 10:

https://backpack.tf/profiles/76561198115233455#!/compare/1587168000/1587254400

https://backpack.tf/profiles/76561198986498652#!/compare/1586822400/1587254400

Bulk

sale 11:

https://backpack.tf/item/6304300235

https://backpack.tf/profiles/76561198058978877#!/compare/1589414400/1589500800

not unusual before this

sale 12:

https://backpack.tf/profiles/76561198042831038#!/compare/1588377600/1588550400

https://backpack.tf/profiles/76561198841279602#!/compare/1588464000/1588550400

QS

sale 13:

https://backpack.tf/profiles/76561198858711453#!/compare/1586476800/1586563200

https://backpack.tf/profiles/76561198208368068#!/compare/1586563200/1586649600

https://backpack.tf/profiles/76561198334598690#!/compare/1586563200/1586649600

untrace then QS

sale 14:

https://backpack.tf/profiles/76561198334598690#!/compare/1587340800/1587427200

https://backpack.tf/profiles/76561198100048802#!/compare/1586390400/1588032000

Untrace

sale 15:

https://backpack.tf/profiles/76561198880949264#!/compare/1575849600/1588118400

https://backpack.tf/profiles/76561198841279602#!/compare/1588291200/1588377600

QS

sale 16:

https://backpack.tf/profiles/76561198220612564#!/compare/1590278400/1590451200

https://backpack.tf/profiles/76561198400492976#!/compare/1590364800/1590451200

QS

sale 17:

https://backpack.tf/profiles/76561198340634356#!/compare/1588723200/1588809600

https://backpack.tf/profiles/76561198020673987#!/compare/1588723200/1588809600

https://backpack.tf/profiles/76561199008475806#!/compare/1589414400/1590451200

https://backpack.tf/profiles/76561199018021198#!/compare/1590451200/1590537600

untrace

sale 18:

https://marketplace.tf/items/tf2/30844;5;u3001

$6.7 / $1.69 = 3.96 keys <--- https://backpack.tf/item/6512822129

$6.22 / $1.69 = 3.68 keys <--- https://backpack.tf/item/7975795236

$6 / $1.69 = 3.55 keys <--- https://backpack.tf/item/6253960862

$6 / $1.69 = 3.55 keys

$6 / $1.69 = 3.55 keys

$6 / $1.69 = 3.55 keys <--- https://backpack.tf/item/6509494788

$6 / $1.69 = 3.55 keys

$6 / $1.69 = 3.55 keys

$6 / $1.69 = 3.55 keys

$8.9 / $1.77 = 5.03 keys

$8.9 / $1.77 = 5.03 keys

$8.99 / $1.77 = 5.08 keys

$9.69 / $1.82 = 5.32 keys

$16.9 / $1.89 = 8.94 keys

Bot.tf:

https://bot.tf/stats/item?def=30844&q=5&ef=Showstopper&craft=1&aus=0&ks=0

1 @ 4 keys

1 @ 3.70 keys,

1 @ 3.30 keys

Total sales @:

3

3.3 (x2)

3.55 (x7)

3.7 (x2)

3.95

4

5.05 (x2)

5.1

5.3

8.95

buyers up to 3.2 keys, only 2 of them.

3 sellers at ~3.65 keys,

https://bot.tf/stats/listings/4EP791GQ

https://bot.tf/stats/listings/Y9Q7V6Z6

seller at ~3.7 keys unsold for a month, unsold for 5 for much longer.

https://bot.tf/stats/listings/4EPK9XQ6

unsold for a month+ for ~3.85 keys,

Cashew's Part:

With those unsolds and the current sellers as low as 3.5, I'm not a huge fan of including 4.

New sales:

https://backpack.tf/item/8374281503

Not unusual during traceable sales

https://backpack.tf/profiles/76561198400492976#!/compare/1591833600/1591920000

https://backpack.tf/profiles/76561198357976875#!/compare/1591833600/1591920000

Sold for ~3.5 keys

https://backpack.tf/profiles/76561199024214291#!/compare/1590969600/1591056000

https://backpack.tf/profiles/76561198805147561#!/compare/1590364800/1591056000

Untrace

https://backpack.tf/profiles/76561198805147561#!/compare/1591228800/1591401600

https://backpack.tf/profiles/76561198358296372#!/compare/1591315200/1591401600

QS

https://backpack.tf/profiles/76561198841279602#!/compare/1591315200/1591401600

https://backpack.tf/profiles/76561198109149008#!/compare/1591142400/1591401600

Untrace

https://backpack.tf/profiles/76561198841279602#!/compare/1591056000/1591142400

https://backpack.tf/profiles/76561198050518375#!/compare/1591056000/1591142400

Sold for 3.55 keys

https://backpack.tf/profiles/76561198986498652#!/compare/1591142400/1591315200

https://backpack.tf/profiles/76561198046393528#!/compare/1591056000/1591228800

Untrace

https://backpack.tf/profiles/76561198046393528#!/compare/1591056000/1591228800

https://backpack.tf/profiles/76561198156171221#!/compare/1591401600/1591920000

Untrace

https://marketplace.tf/items/tf2/30844;5;u3001

$7.2 / $1.92 = 3.75 keys

$10.89 / $1.99 = 5.47 keys

$11 / $2.03 = 5.41 keys

$7.20 / $2.03 = 3.54 keys

4 new sales supporting under 4, 2 for higher than 5.

https://bot.tf/stats/listings/MXXNODW6

Josuke has been unsold at ~3.65 keys for over a month now,

https://bot.tf/stats/listings/MGLXOQD7

Seller at ~3.5 has been unsold for about a week.

I'd probably keep 3.3 in the range still, so 3.3-3.75 or something along those lines