Calculation of average cost of shares for promoters

In IPO ads I see that average cost of acquisition of equity shares for promoters would be very very less (Rs 1 or 2 and sometimes even in paise). I want to how is this possible and how is it calculated?

Even company is formed than shares are allotted to promoters at par (=book value at that time) of Rs 10 / share.

So average cost of acquisition for promoters should be Rs 10/share... no?

Any help?

Calculation of average cost of shares for promoters