Resuggest under Mindacos' comments:

Range is way too wide here, it also doesn't help that the 42 key sale is pro ks.

While we do allow for pro ks sales to be used on collector's items, it doesn't justify having a range this big.

Considering there's also a very low sale at 8.45, you can rule both out as outliers and go with 22 flat.

Past month

MP: https://marketplace.tf/items/tf2/413;14

$39.99/1.85=21.6k

SCM: https://steamcommunity.com/market/pricehistory/?country=US&currency=1&appid=440&market_hash_name=Collector%27s%20Professional%20Killstreak%20Solemn%20Vow

$97.32/2.33=41.8k (too high)

$19.36/2.29=8.45k (countered by buyers)