TF2 Trading #2: What determines prices?

I've had people ask me before "Who sets the item prices?" I usually look confused for a moment, then inform them that no one does. Which usually makes them look equally confused. I'm told my attempts to explain economics generally doesn't improve the situation either.

In reality though, TF2 is no different than the free market in the real world -- supply and demand. Another way to word that would be availability and desirability. But that's a little too simplistic. So what exactly are the factors that make up "supply/availability" and what exactly constitutes "demand/desirability"?

TF2 Supply of <Your Item Here> is influenced by

• Number of <your item here> in the game
• Speed at which more <your item here> will come into the game
• Cost of getting <your item here> outside of trading -- e.g. the Mann Co Store, pre-ordering another game, opening a crate, or some other non-trading venue
• Likelihood of Robin Walker deciding to celebrate National Aboriginal <Your Item Here> Day and giving everyone <your item here>
• Likelihood of Robin Walker being in a bad mood and deleting everyone's <your item here>

TF2 Demand of <Your Item Here> is influenced by

• Number of people who want <your item here>
• Number of people who already have <your item here>
• How badly people want <your item here>
• Likelihood of Robin Walker announcing that <Your Item Here> is [Totally Awesome | Totally Sucks]

Fortunately for us, Robin Walker is pretty passive, so we don't have to worry about him much. Those other factors matter a lot though.

Let's take some examples here using just our brains and the above principles.

Which Is More Valuable: A Crate or a Weapon?

A weapon: Almost no one has keys, so those crates are just taking up space. With the exception of the first day or so that new crates are released, no one wants crates. With a weapon, at least you can smelt it into metal.

Which Is More Valuable: Drably Olive paint or White (abundance of tinge) paint?
White: White looks great on a lot of hats so lots of people want it, whereas olive looks not so good, so rarely anyone uses it.

Which Is More Valuable: Vintage Killer's Kabuto or Non-Vintage Killer's Kabuto?
The vintage kabuto: There's fewer of them, there will never be any more, and people want them because owning vintage makes you look more experienced (or so I've been told).

Which Is More Valuable: Stormy Storm Hustler's Hallmark or Circling Peace Sign Hustler's Hallmark
The Stormy Storm: It's a brand new effect, so there's fewer of them and there's a novelty of owning one of the latest and coolest effects.

Which Is More Valuable $1.50 USD or a Mann Co Crate Key?

The Key: If I was able to sell the key for $2 to someone who wanted to open a crate, I'd be making 50 cents, and he'd be saving 50 cents over buying it from the store.

Just like a real economy, supply/demand really do determine prices in TF2. There really isn't a magic guy sitting behind the scenes making up values after all!