Hi CooperBox,
There's a big chance I'll update the model a bit to make it fit easier. The connection with the IDE-connector of the Cube itsself is very tight. Using the 'smaller' adapters I should be able to make it an easier fit.
www.benl.ebay.be/itm/201401876931
As far as to printing services, I think "3D-printing stores" are really for professionals (architects, ingeneers, etc..) Hobbiyst can use
www.3dhubs.com
There you can get consumer 3D printer owners to print your stuff, that should be cheaper.
As far to answer your questions:
i) I think that's fairly steep, probably they also charge a start-up cost. Depends on the material as well, PLA or ABS? (or other?)
ii) I think the price for a professional print would be pretty steep, it would consist of perfect edges, no printer markings on the print itself. In short: a high quality item (which looks stunning). A non-professional print would not have this 'perfect' finish, and be rougher at the edges, but who cares. The bracket is not visible anyway.
iii) Hehe, I live in Belgium
If I would print it, i think the bracket would cost less than €5 in materials and electricity (mostly electricity). Could try to calculate it, but this is a gut-feeling-cost.
Remember the Parism brackets for another optical drive installment, it would be fairly easy to design this and make an open-source 3D-modal for this. Even the spirica heatsinks (for VRM, or graphic cards) could be transformed into a open-source 3D-modal (but those would have to be cnc'ed out of metal). To bad these open source technologies got a bit to late into the party. Cube modding would have been completly different if the 3D-printing technology was as develop as it is today.