Can Anyone help me to buy a system on chip solution for tablets? what is the best performing and affordable solution?

How much those system on chip solutions cost? how can we get it and test it? any help topics or references can be shared please. I am looking forward to develop a low cost embedded system for my own application developments. Please share me some details

There is no real system on a chip system for tablets. Most of them build there custom main boards around an arm based processor. What you need to start looking at are all the different development board that are available. No one board is going to have everything your looking for but many will offer the ability to add the features and electronics you want.
Element 14 also has a main page that can help you find the development kit that will best suite your needs. Plus other peripherals and software to help get you started.

http://www.element14.com/community/community/knode/dev_platforms_kits
Unless you want millions, or at least 10s of thousands, there is NO way developing your own tablet can possibly be cost effective.