almost every ICO token is with lower price when go to exchange after ICO ends.
That is not true. Some ICO tokens get to gain above 100% growth when they hit the market if they have a pretty strong base - which means if their project is attractive and their ICO has been actually successful but not faked, then they are likely to get a rise when they are listed in exchanges. So people buy the tokens in ICO phase to get profits when the token is listed in the markets and gets to a higher price than they bought them in.