Does it matter spend 7300$ for Nikon D3X while D5200 is 6500$ cheaper?

Does it matter spend 7300$ for Nikon D3X while D5200 is 6500$ cheaper? I compared the main differences betwen both and it lands on the CMOS sensor size: 35, 9 x 24, 0mm (FX) for D3X and 23, 5 x 15, 6mm for D5200.

Is it really worth 6500$ in price for about 12 x 8 mm difference in sensor size?

Are there things i could achieve with D3X that i can't with D5200? I sincerely apologize if my question is too rookie, thats exactly what i'm when it comes to professional photography.

The D3X is definitely better:
http://snapsort.com/...-Nikon_D3X

Frankly though, they're not 2 cameras that really compete with each other, as their huge price difference puts them in different brackets. Until you're experienced enough to know why the D3X is better and more expensive, a D5200 is going to be MORE than enough camera.

In the right hands, a D5200 is capable of producing excellent results

What do you want to do with it? A D3X is a popular camera for studio work. It has a higher flash sync speed than a D5200.It can shoot more FPS. It will have better color depth and a higher dynamic range if you're processing in RAW. It is also built a lot tougher and you get dedicated buttons as opposed to having to go through the menu. Noise is reduced also. Most other things picture quality wise are dictated by the lens and not the camera.

If you are having to ask this question, then you don't need the D3X. The answer is truly that simple.