You would think there would be a raise with the buyers here...

Sales

Sale 1: Untrace

https://backpack.tf/profiles/76561198188176697#!/compare/1596326400/1596672000

https://backpack.tf/profiles/76561197968465515#!/compare/1596326400/1596585600

Sale 2: Sold for 18 keys

https://backpack.tf/profiles/76561198080179568#!/compare/1597190400/1597276800

https://backpack.tf/profiles/76561197999188384#!/compare/1596240000/1598140800

https://bot.tf/stats/listings/MVQZ8JZV

Sale 3: Untrace

https://backpack.tf/profiles/76561198378224492#!/compare/1585612800/1596844800

https://backpack.tf/profiles/76561198080179568#!/compare/1596758400/1596844800

Sale 4: Sold for 18 keys

https://backpack.tf/profiles/76561198125791160#!/compare/1597190400/1597276800

https://backpack.tf/profiles/76561198857650831#!/compare/1594598400/1597276800

https://backpack.tf/item/7957589708

https://bot.tf/stats/listings/MVQZ8JZV

Sale 5: Sold with TW Tossle Cap for 27 keys

https://backpack.tf/profiles/76561198043926315#!/compare/1596672000/1597017600

https://backpack.tf/profiles/76561198125791160#!/compare/1596931200/1597017600

Sale 6: Sold to buyorder of 12 keys~

https://backpack.tf/profiles/76561198098898341#!/compare/1596326400/1596672000

https://backpack.tf/profiles/76561198363395191#!/compare/1596240000/1596326400

https://bot.tf/stats/listings/YD1XV53V

Sale 7: Sold with something else for 25 keys

https://backpack.tf/profiles/76561198850178158#!/compare/1599868800/1599955200

https://backpack.tf/profiles/76561198255647997#!/compare/1599609600/1600387200

Buyout was 13~

https://bot.tf/stats/listings/466D787R

Sale 8: Sold for Circling Peace Sign El Zapateador + 1 key

https://backpack.tf/profiles/76561198092554004#!/compare/1598918400/1599177600

https://backpack.tf/profiles/76561198176670029#!/compare/1598659200/1598918400

Using there.

Sale 9: Sold for 15 keys

https://backpack.tf/profiles/76561198061127604#!/compare/1598140800/1598313600

https://backpack.tf/profiles/76561198092554004#!/compare/1598054400/1598400000

Sale 10: I counted 11 keys from the buyers side.

https://backpack.tf/profiles/76561198384047845#!/compare/1597968000/1598140800

https://backpack.tf/profiles/76561198061127604#!/compare/1597881600/1597968000

But since the seller first purchased for 13, I think there was something else added.

Sale 11: Sold for 13 keys~

https://backpack.tf/profiles/76561198119634686#!/compare/1594252800/1594339200

https://bot.tf/stats/listings/Y3WP8LDQ

Sale 12: Untrace

https://backpack.tf/profiles/76561198315845408#!/compare/1599696000/1599782400

https://backpack.tf/profiles/76561198363395191#!/compare/1599609600/1599696000

Buyorder of 12 keys~

https://bot.tf/stats/listings/M0O66JWZ

Sale 13: Sold for 14 keys

https://backpack.tf/profiles/76561198850178158#!/compare/1599004800/1599091200

https://backpack.tf/profiles/76561198315845408#!/compare/1599004800/1599091200

Sale 14: Untrace

https://backpack.tf/profiles/76561197995822698#!/compare/1597622400/1597708800

https://backpack.tf/profiles/76561198850178158#!/compare/1597622400/1597708800

Sale 15: Untrace

https://backpack.tf/profiles/76561198203000900#!/compare/1597363200/1597449600

https://backpack.tf/profiles/76561197995822698#!/compare/1597363200/1597449600

Sale 16: Untrace/Bulk

https://backpack.tf/profiles/76561198269337198#!/compare/1597363200/1597449600

https://backpack.tf/profiles/76561198203000900#!/compare/1597276800/1597363200

Sale 17: Untrace

https://backpack.tf/profiles/76561198129922212#!/compare/1558310400/1597363200

https://backpack.tf/profiles/76561198269337198#!/compare/1597276800/1597363200

Sale 18: Untrace

https://backpack.tf/profiles/76561198419584303#!/compare/1597363200/1597449600

https://backpack.tf/profiles/76561198129922212#!/compare/1558310400/1597363200

Sale 19: Untrace

https://backpack.tf/profiles/76561198358851292#!/compare/1597276800/1597363200

https://backpack.tf/profiles/76561198419584303#!/compare/1597276800/1597363200

Sale 20: Untrace

https://backpack.tf/profiles/76561198438712831#!/compare/1597276800/1597363200

https://backpack.tf/profiles/76561198358851292#!/compare/1597190400/1597276800

Sale 21: Sold for 14 keys

https://backpack.tf/profiles/76561198080179568#!/compare/1596499200/1596585600

https://backpack.tf/profiles/76561198438712831#!/compare/1596326400/1596585600

Sale 22: Untrace

https://backpack.tf/profiles/76561198136097697#!/compare/1594684800/1595462400

https://backpack.tf/profiles/76561198080179568#!/compare/1594598400/1594684800

Marketplace

https://marketplace.tf/items/tf2/99;5;u57

July

$33.33 on July 19 (33.33/1.97 = 17~)

https://manic.tf/keyprice/?at=2020-07-19

33.33 on July 22 (33.33/1.94 = 17~)

https://manic.tf/keyprice/?at=2020-07-22

August

$27.95 on August 12 (27.95/1.84 = 15~)

https://manic.tf/keyprice/?at=2020-08-12

27.95 on August 28 (27.95/1.85 = 15~)

https://manic.tf/keyprice/?at=2020-08-28

September

$24.75 on September 6 (24.75/1.83 = 14~)

https://manic.tf/keyprice/?at=2020-09-06

25 on September 7 (25/1.83 = 14~)

https://manic.tf/keyprice/?at=2020-09-07

26.39 on September 20 (26.39/1.85 = 14~)

https://manic.tf/keyprice/?at=2020-09-20

Classifieds

https://gyazo.com/3b0cb2b03dd16075e64f9dbf77e0a8fe

https://gyazo.com/e70f29573a3e4bbc76199758bd4b092c

Buyers up to 15.

Summary

Sales at 12, 12, 13, 13, 14, 15, 18, and 18.

Marketplace sales at 14, 14, 14, 15, 15, 17 and 17.

Conclusion

Going to exclude 12 and 13 here, as they are far under buyers.

Although 14 and 15 are also under buyers, there are 4 sales at 14, and 3 at 15. They are common enough to include here, and the sales at lower also support my low end here.

Going with 14-18 here.