Let's start getting some prices for these Smissmas 2019 hats, shall we?

I believe this is the only one in existence and the only sale I could find, sold for 563,50€ on the Steam Community Market on January 19, 2020:

https://i.imgur.com/h8CsB0n.png

https://i.imgur.com/7WrC2AQ.png

https://i.imgur.com/mBWicHK.png

https://backpack.tf/profiles/76561198044065256#!/compare/1578960000/1579392000

https://backpack.tf/item/8398854468

https://steamcommunity.com/market/listings/440/Unusual%20Smissmas%20Saxton

The price of Keys on the SCM fluctuated between 2,20€ and 2,23€, giving us a median of 2,215€ per key.

https://steamcommunity.com/market/listings/440/Mann%20Co.%20Supply%20Crate%20Key

563,50€ divided by 2,215 gives us 254,4, which would come up as 254 Keys. However the backpack.tf Unusual Price Suggestion Rules says that "for hats 200-1000 keys, please round to the nearest 10 keys", giving us the final value of 250 Keys.

https://forums.backpack.tf/topic/6033-rules-for-unusual-price-suggestions/

Hopefully me using local currency as euros instead of USD is alright, Steam is a bit silly when it comes to currencies and whatnot depending on your location. Using USD would give us $624,97 divided by 2,455 (Keys fluctuated between $2,44 and $2,47 on Jan 19) giving us 254,57~ so the final amount I believe would still stay at a nice and even 250 Keys.

Please let me know if I've made any mistakes or if there have been any other Snowblinded Smissmas Saxton sales I haven't taken into account, so I can make a revised suggestion in the future if need be!