Credits La Tuya and Xergoyf

Bought it for $ 250 - https://mannco.store/item/440-glowing-fireworks-unusual-soda-cap

$250 / $1.78 = 140 Keys

Sold it for $500 - https://marketplace.tf/items/tf2/31265;5;u237

$500 / $1.95 = 256 Keys

Trade 1:2 - https://backpack.tf/profiles/76561198141708627#!/compare/1659916800/1660089600

unpriced unusuals so idk

History - https://backpack.tf/item/11936433648

Xergoyf:

The two unpriced unusuals have been sitting unsold at 75 and 60 respectively for 4 months.

https://gyazo.com/55e4089f7292f80275046ac5dc2e31bd Shelmet at 75

https://gyazo.com/ac22b228f06aec218c32e89076f0cc0c - Field at 60

That makes that sale 135 at most, but likely much less. With that in mind 256 is definitely an outlier here.

Regarding the 140 sale, your key price is slightly off. It was 1.72 at the time of the sale, so we should use that price: https://mannco.store/item/440-mann-co-supply-crate-key

That makes the sale 145

145 flat will work here.