I bought this today for 100 keys mixed.

The following are the only recent sales and movements in the past 3 months

Sale 1:

Offered 1 Max’s Head, painted black (~ 29/30 keys, https://backpack.tf/stats/Unique/Max%27s%20Severed%20Head/Tradable/Craftable shows currently priced at 29.7-29.8, but B/Os are lower at 29. However it is painted so the price of this fluctuates) + 70 keys pure:

Seller:

https://backpack.tf/profiles/76561198403706199#!/compare/1647043200/1647216000

(History shows that he initially received 69 keys, I sent the 1 key remaining since I forgot to thus appears as separate)

Buyer: https://backpack.tf/profiles/76561198300039170#!/compare/1647129600/1647216000

(doesn’t show much, many trades on the day)

Sale 2 on Mannco.store

https://mannco.store/item/440-sulphurous-unusual-detective-noir

Sold for 160 USD, and mann co. keys were for $1.61 on the day of the sale; on the 15th of January (https://mannco.store/item/440-mann-co-supply-crate-key)

160/1.61 = 99.4. This can be rounded to 100.

Even if you factor the other prices (29 keys for the Max’s head), it can be rounded to 100 keys.

There’s a 3rd sale that occurred in the 1st of Jan, but it’s untraceable as I can’t find anything on the seller’s side, and the buyer had 2 trades that day so the number may not be accurate. I’d say it’s best to ignore this or consider it an outlier.