Month 1 https://gladiator.tf/sales?item=Holy%20Grail%20Taunt:%20Second%20Rate%20Sorcery&at=2022-03-04T15:57:11.653Z

1 @ 5 keys 10.22 ref

1 @ 5 keys 11.66 ref

1 @ 5 keys 18.55 ref

1 @ 5 keys 25.33 ref

1 @ 5 keys 34 ref

Month 2 https://gladiator.tf/sales?item=Holy%20Grail%20Taunt:%20Second%20Rate%20Sorcery&at=2022-02-04T15:57:11.653Z

Nothing

Month 3 https://gladiator.tf/sales?item=Holy%20Grail%20Taunt:%20Second%20Rate%20Sorcery&at=2022-01-04T15:57:11.653Z

1 @ 4 keys 34.33 ref

1 @ 5 keys 3.33 ref

https://marketplace.tf/items/tf2/30816;5;u3003

$9.99 / $1.83 = 5.46 keys

$9.99 / $1.81 = 5.52 keys

$9.99 / $1.78 = 5.61 keys

https://mannco.store/item/440-holy-grail-unusual-taunt-second-rate-sorcery

$8.27 / $1.64 = 5.04 keys (x2)

$9.99 / $1.63 = 6.13 keys

$9.99 / $1.61 = 6.20 keys

$9.99 / $1.60 = 6.24 keys

Classies: https://gladiator.tf/listings/622234055d6fad5e65cb12cb

Buyers at ~4.5, sellers ~5.5-6+

4.5-6 keys seems okay. Other alternative would be 5-5.5, which gives the same midpoint.