Because youre kiding yourself if you think it'll be worth heaps for starters, even cars like this that are not original don't make big money and it's probably got alot more 500 parts on it than this shell ever will have again.
http://www.pistonheads.com/sales/2425512.htm
So you buy a shell with ID, what about the other premium priced parts you need to get to go with the shell to make it even 50% of the car it's suposed to be, and it'll still be known to be a car that was broken and probably had poor history before hand (hence why it was broken).
What are you essentially buying at the end of the day, a 3dr shell that has a slightly different number and it says rs500 on the V5, I'm not saying I wouldn't buy it, only that I wouldn't be getting a semi and parting with all my hard earned cash when I could go and get a 3 dr and put on aftermarket spoilers/bumper for probably less than half the price.

Each to their own, I hope the seller gets their asking price and the buyer is happy with their "Rs 500".