This mighty item needs its own Tier on the tierlist for obvious Reasons, Getting a Gpan is impossibly Rare and its price is due to this fact. it usually drops with Professional killstreak addition, and its price varies around= 3000 Keys+

In This Tier, We only have The Australium Eyelander, which has a way lower drop rate compared to other australiums, making it more expensive.
Average Price: 71-72 Keys

In This tier, we have 3 drops, that is really Decent in price, just not as good as an Eyelander, consider yourself lucky if you manage to get one of these. (The australiums on the Left are sligthly more expensive than the ones on the right, example: Medigun>Scattergun)
Strange Australium Medigun Average price: 50-52.5 Keys
Strange Australium Rocket Launcher Average price: 49-51 Keys
Strange Australium Scattergun Average price: 44.5-45 Keys

These ones are Still pretty decent, they could be better, but definitely not bad, and many people would be really happy with these.
Strange Australium Wrench Average Price: 36.5-37.5 Keys
Strange Australium Sniper Rifle Average Price: 34.5-35 Keys

in this tier, we have items that varies around 20-28 keys, These ones are meh, enough to satisfy most people and clearly way better than Some aussies.
Strange Australium Minigun Average Price: 27-28 Keys
Strange Australium Flamethrower Average Price: 24.5-25 Keys
Strange Australium Stickybomb Launcher Average Price: 23.5-24.5 Keys
Strange Australium Tomislav Average Price: 22-24 Keys
Strange Australium Knife Average Price: 21-22 Keys
Strange Australium Grenade Launcher Average Price: 20-21.5 Keys

This Tier is Pretty trash, loot is most of the time not worth the time and tours if you are high tour, it can still be worse, but still a bad one.
Strange Australium Frontier Justice Average Price: 17.5-18 Keys
Strange Australium Force-A-Nature Average Price: 17-18 Keys
Strange Australium Black Box Average Price: 15.5-16 Keys

This tier... This tier includes the WORST possible Drops on mvm for australiums, it might still be an australium Nonetheless, but i would rather get a prof killstreak Kit fabricator instead of these.
Strange Australium Ambassador Average Price: 13.5-14 Keys
Strange Australium SMG Average Price: 12.5-13 Keys
Strange Australium Axtinguisher Average Price: 8.5-9 Keys
Strange Australium Blutsauger Average Price: 7.5-8 Keys

Strange Professional Killstreak Golden Pan Average Price:3000+ Keys
Strange Australium Eyelander Average Price: 71-72 Keys
Strange Australium Medigun Average price: 50-52.5 Keys
Strange Australium Rocket Launcher Average price: 49-51 Keys
Strange Australium Scattergun Average price: 44.5-45 Keys
Strange Australium Wrench Average Price: 36.5-37.5 Keys
Strange Australium Sniper Rifle Average Price: 34.5-35 Keys
Strange Australium Minigun Average Price: 27-28 Keys
Strange Australium Flamethrower Average Price: 24.5-25 Keys
Strange Australium Stickybomb Launcher Average Price: 23.5-24.5 Keys
Strange Australium Tomislav Average Price: 22-24 Keys
Strange Australium Knife Average Price: 21-22 Keys
Strange Australium Grenade Launcher Average Price: 20-21.5 Keys
Strange Australium Frontier Justice Average Price: 17.5-18 Keys
Strange Australium Force-A-Nature Average Price: 17-18 Keys
Strange Australium Black Box Average Price: 15.5-16 Keys
Strange Australium Ambassador Average Price: 13.5-14 Keys
Strange Australium SMG Average Price: 12.5-13 Keys
Strange Australium Axtinguisher Average Price: 8.5-9 Keys
Strange Australium Blutsauger Average Price: 7.5-8 Keys

Thanks For reading my guide, i hope i could help.