Okay, first suggestion and a new way of giving proof because clearly looking at sellers and buyers does not work. People look for profit that means selling above the accepted price and buying below it. If we follow these rules we'll only inflate the economy.

Here's proof of an inflating economy:

Sellers:

http://www.tf2outpost.com/trade/23798941 Selling 11.88

http://www.tf2outpost.com/trade/23505659 Selling 11.77

http://www.tf2outpost.com/trade/22549940 Selling 11.55

http://www.tf2outpost.com/trade/23825676 Selling 12.00

http://www.tf2outpost.com/trade/23864117 Selling 12.00

http://www.tf2outpost.com/trade/23815600 Selling 11.88

http://www.tf2outpost.com/trade/23613227 Selling 12.00

http://www.tf2outpost.com/trade/23871106 Selling 11.77

http://www.tf2outpost.com/trade/23812642 Selling 12.00

http://www.tf2outpost.com/trade/23695181 Selling 11.66

http://www.tf2outpost.com/trade/23848299 Selling 11.66

Buyers:

http://www.tf2outpost.com/trade/23746501 Buying 10.66

http://www.tf2outpost.com/trade/23609050 Buying 10.00

http://www.tf2outpost.com/trade/23201623 Buying 10.00

http://www.tf2outpost.com/trade/23111547 Buying 9.33

http://www.tf2outpost.com/trade/23085627 Buying 11.00

http://www.tf2outpost.com/trade/23831182 Buying 11.00

Considering the current agreed upon price 11.33-11.44, this current economy will only rise in price from the demand of sellers. If we consider this to be the only proof we can give then the price should now be 11.55-11.66. Now here comes the interesting proof:

Let's convert 1 TF2 Refined into WoW gold, yes that's right, WoW gold.

Playing on a US server you can get 5000 gold for $4.83.

http://us.online-gold.de/World-of-Warcraft/WoW-Gold,US,Aegwynn-Alliance/ 5000 for $4.83

http://www.tf2calculator.com/ Using TF2Calculator's prices for Ref and Key

So how much Gold could we get for a Refined?

5000/4.83*0.2= 207.039337474

How much could we get for a Key?

5000/4.83*2.24= 2318.8405797

How much should Ref be?

2318.8405797/207.039337474= 11.180880694

Now, in USD:

2.24/0.2 = 11.2

That incremental 0.02 means quite a bit, it means you're essentially giving a scrap for free or a refined in bulk buy cases.

So I used WoW simply because of how precise the numbers end up being, you can see if an object needs raising in price or lowing simply due to the exact decimal places and cause it was cool :3

Now, I think keys price should be lowered even further than 11 ref, but for the evidence I can give, 11 ref seems a good start. I'll probably be back, if you guys like my unique proof to give hopefully an even better suggestion with even more interesting figures. :)

And a final note, hopefully I've inspired you guys to stop using this 'buyers' and 'sellers' proof technique because that ends up in massive inflation due to people wanting profits.