I remember one time an admin said "NO" to a "lower a key's price" when the voting has a higher percentage approving of the lowering of the price, I'm sure you can find that story on the interwebs.
I have a few notations on how they can be corrupt, too. The admins that made money off of keys can make an alt that can sit there for 3 months, trade the keys to that alt then ask to increase the price of keys where the admin on his main account could approve of the submission he made himself on his alternative, and maybe make alternative accounts to vote for the increase of key price as well.
That being said, bp.tf is the number one reason why the key price inflated, and why it's a problem.
First off, try to sell a big kill back then and then try selling one from now. Back then when keys were 2.33 refined, you could sell a big kill for 15 keys. Keys on mann. co store cost $2.49. That being multiplied by fifteen equals $37.35 In equation, that is $2.49 X 15 = $37.35
Now, since the big kill is twelve keys, and Mann. co keys can be sold on market but the prices there always change, lets stick with $2.49. $2.49 times 12 equals $29.88, meaning you actually can profit a lot less from the item from then and now because of the price drop.
So, that was before backpack.tf existed. You can say that you would be scammed by the site, yes you can. Since the web site itself is heavily advertised in VARIOUS servers, people that do go to the website (backpack.tf) will also see an advertisement to the right of the screen. Therefore BP.tf makes money off of those advertisements. People often like to have a reference sheet, and they'd supply BP.tf with ad money.
Now, there is another website called "Scrap.TF", made by the same people. Even though BP.TF lists the price of keys to be 7.11 to 7.22, they are buying keys for 7.33, where they added just one-two scrap metal. Then you can see that they are selling keys for 7.55, just added three to four scraps. That doesn't seen fair at all, considering that these are the same guys who owns BP.tf. So they are profiting off of advertisements, profiting off of your own metal, and your own keys which appears to be highly corrupt and unfair at all.
You don't get to make profit at all at this time, you just won't be able to. Remember the one "TF2Spreadsheet" site back then? They used to price keys at 2.33 refined because in their philosophy, "rarity increases price". It made a lot of sense for keys to be sold at that price because of how ridiculously common keys are and still are being bought from the Mann. co store. Keys have usually been the top-seller of the Mann. co store.
In the meantime, everything else including unusuals are decreasing in price because of bp.tf, making the sellers make a lot less profit, as a notable example is for those merchants trying to trade their big kills for 15 keys to get $40, will only actually get $20.
TF2Spreadsheet kept keys at 2.33 because keys are still the most purchased item. Mann. Co sells an infinite supply of keys, no way you can run out of keys over the limited big kills that are being sold at a significantly lower price than usual.