Maybe it's just me, but if you have something listed, with a reasonable profit margin, then why all the faff about grouping things together, just to save a little extra money?
ie. if you where happy with what you making on a single item, why wouldn't you be happy to send them as single items?
Unless the customer has grouped together an order, the only person benefitting from doing this kind of thing is the seller! Not exactly customer centric is it?
Why try to work around a perfectly workable system?