Has thought been given as to how this would be implemented? I do point of sale development, and see this fitting neatly into the way 'modifiers' work in a restaurant POS system.
For example a steak might have three modifiers required, temperature (rare, med rare, etc), starch choice (Mashed potato, rice, etc) and vegetable choice (Salad, asparagus, etc)
The configuration is you set up a top level table of modifier groups, in this example Temperature, Starch and Vegetable. You then configure the modifiers themselves, assign them to groups, and add additional costs if required. (Possibly an upcharge for the asparagus in our example)
You configure the steak item, and check that it requires a choice from these three modifier groups. On a POS system the system walks the server through the order, but in the web ordering world we would probably display comboboxes populated with the items in the groups associated with the parent item. If they choose a priced item, the additional charge displays with the modifier so they know why the price changed.
There are additional levels of complexity available, but that basic design I see as meeting the majority of the needs I read here. Can anyone comment on what this wouldn't let them do?