The stuff you want is called Jevity. It's a complete liquid diet that's used for feeding tube patients (Ebert after cancer being one of the most famous). It can be consumed orally, and you can buy it in bulk from Amazon. It's been designed by people who are experts in nutrition and has been used for years by patients as a sole food source.
Of course, Jevity only claims to keep you alive and healthy as your only food source, not to trim your fat, sharpen your brain, etc. But I'm fairly sure that has more to do with ethics, a basic knowledge of the subject, and an understanding of the necessity of double blind studies for medical claims than someone finding out the secrets to perfect health who forgot iron and sulfur in their supplement.
Looks like it is 1c/cal. $20/day is not reasonable.
Rob Rhinehart's food replacement Soylent now has a crowdfunding campaign.
If you're interested in one or more of these benefits, send in some money! There is also a new blog post.