Custom Fee Field problem

I have Events Booking component in the site. Event is free, but there are some possibilities, what can be choosen and these posibilities costs. Now I have defined Custom Fee Fields for the possibilities. When user makes Individual Registration, then all the choosen possibilities are correctly summarized. But when user wants to register a group, then posibilities on the Custom Fee fields are not summarized. Registrant sees, that he has to paid 0.00 money, but by group registration he has chosen some possibilities, that costs. When to register a group, then it's not important to collect group members data. We allow register a group, but in the group every member should have the same options, so in the group, when possibilities are choosen, the sum should simply to be multiplied by number of group members.
See the picture about issue: