Dude, Dota economy 101. If you want a specific item that comes from a chest which is valuable in the market, always sell some chests, make some money and buy the item. Unless you are that lucky 0.01%, you will never get a high tier item like Battlefury or Shadow Blade. I sold all my Bloom Bounties and now have a decent amount of wallet with which I can buy any high tier item I want.
Next, you didn't read the chest description. It says you will get a mythical and above. Throe is a mythical courier, not rare. There are a lot of really cheap mythicals like this, which makes it very hard to actually get the item you want. I didn't open any chests, but bought the mythical Luna Avon mount, Coco the courier, AntiMage rare weapons, a mythical Death Prophet Crown Of The Death Priestess headgear, and all of these for less than $3 from the market.
Summary, unless you sacrificed a lamb to the Dota gods in the morning, don't open chests.