The cost of the bodykit would depend on your requirement,the body parts want moded etc. A beat barell would cost between 5k-8k.
The Price of the paint too depends on the type of the paint you are going to use something like Pearlescent paint job would be costly.cost of interior also depends on the material you are gonna use (Leather or fabric).For interior you can add a sports steering and Shift knob. Used bucket seat sets cost between 25k-45k. The cost of the sound system depends on the Head unit,Amplifier,speakers and the Subwoofer you are gonna use.I would advice you to stick to 15" alloys because U'll need to use very low profile tires if you use 16" or 17" which will in turn make the ride rough and uncomfortable.
The best thing is to plan how you want your car to look like and then get estimates from the modification guys .