I don’t quite follow what the loophole is here. A customer can already upload multiple models to an order, and therefore only paying the start up costs once for the entire order of multiple parts. This is working as intended. The quote will be correct for the models, because we calculate on sliced volume, and the price of the combined model, will simply be the same as the price of all the individual models.
As a matter of fact, a lot of Hubs already do what this customer has done. To maximise their build volume, they print multiple things at the same time, whether they are personal projects, or printing different orders at the same time. Lots of Hubs, when faced with an order of a ton of different, small parts, will combine them themselves in order to maximise their printing potential, and save on time.
I genuinely believe that your customer was merely trying to be efficient, or perhaps do some of your prep work for you. If you could please elaborate what part of the customer handling his printing this way is unfair or exploiting the system, then I will raise the issue with my superiors.
Benny - 3D Hubs Customer Support Agent