Originally Posted by AndyPhamVN
1. Where there is demand, there will be supply.
2. Some people are impatient, so they might sacrifice everything to get just one key.
3. Some people have imperfect knowledge about the Dota 2 buy-and-sell system (they don't know how much a key costs and a rare item costs).
4. Some key sellers are greedy.
That bold line is the main reason. Even more so with all the new item sets that dropped a few weeks back. People throwing 1 Rare + stuff for one freaking common. They are the cause of why people sell high.
Now 3 weeks have passed, and using only the excess commons I have accumulated, I got about 20+ new commons. I got all of them using only 1:1 common trade. The first few weeks of trading was horrible, as you get idiots posting in your trade saying "HAHAHA THIS COMMON MEEPO ITEM IS WORTH AT LEAST 3 RARES! STOP TRYING TO SCAM PEOPLE!!! XAXAXA~"
People will not be able to sell high if people don't overpay their stuff. Sadly, this is DotA community, and getting people to cooperate is impossible. So the only thing to do is to be patient and wait it out.
By the way, if you want to know why treasure keys got shoot up by so much, it is simply because of this chest:
You can open this chest by any normal treasure keys from the description. And the worst items you can get from this chest are the Grand Blade and Cape of Dark Magic. The Cape is highly sought after, while the Grand Blade is still at least a rare. The other items in this chest have just freaking high demand.