Well, I've been following this unusual for a long time, I still don't know exactly how to show "evidence" to support my suggestion, so I can only leave my experience in the few months that I was hunting this unusual.

-I have only seen 2 occasions where this unusual was published for less than 37 keys and they bought it quickly

-I bought mine for 45 keys in overpay (40 keys + 1 unusual taunt value in 5 keys in b/o) [proof 1]

-STN shows supply and demand a little better (https://stntrading.eu/item/tf2/Unusual+Jellyfish+Jam+Brothers+in+Blues)

In my personal opinion it is somewhat unfair to pay less than 30 keys for an unusual one that only exists 39 of this effect, I still don't understand what the buy orders are based on, most (if not all) are from bots that do not exceed 30 keys.

Also my suggestion is based on the probabilities of jellyfish effects, with Jellyfish Jam being the most common and Jellyfish Field being the rarest.

Possibly my arguments are not adequate or sufficient to fully support my suggestion, I will be happy to receive your feedback, for the moment this is my suggestion on the price, have an excellent 2024.

Proof 1: https://imgur.com/a/eI54M3s