Buying of equityshares ( @ discounted price)in physical forms

   I came across several people, (  Mostly CA....  as are the ones.. who understand money and its working system..more ) who buy SHARES @ discounted price,  How it works GOOD for them ?

can someone throw more light , on this trading , as BSE website says , this avenue can be used for ONCE only, as those  who BUYS these shares in physical form  has to have there DEMAT account , has to compulsorily DEMAT  those shares to it  TO GAIN ITS FRUITS ,  NO FURTHER SELLING ( 2nd sell or so on ..) IS PERMITTED , I would like to know , How this system works , Like any equity share if TRADING(demat)  online @ 1000, but  Mr.A with jt holding with Ms.B and Mr. C has  those shares in physical form as share certificate , instead opting for , opening a  DEMAT ACCOUNT and FURTHER CONVERSION   of those shares , that can be traded in PHYSICALFORM to MR.LMN ( who  already does have a demat account )at predecided discounted price