Just to share my opinion:
In the current upper watch market (Tag Heuer, Breitling, etc.) where Apple is targeting their watch, for a watch designed with the same metal case, there are several models (one with steel band, other with rubber band and other with leather band), each one are versions of the original model, but the rubber band watch model is cheaper than the leather and the metal band is the most expensive one.
You can buy for instance a rubber model, or the steel band one, BUT for instance if you buy the rubber (band) one and after that you buy only the metal band as an extra, the price for it is absolutely outrageous, meaning that for starters you should have bought the model (watch with band) all in metal/steal in the first place AND after buy the rubber band as an option.
So my thoughts are: Apple will make ALL bands available to buy separately (metal, leather, rubber), but the metal ones will cost $$$$$$, making them primarily bought originally with the watch, and making the watch sold with rubber bands the cheaper model available to public. The positioning of each Watch will be:
Sport Watch (all models with rubber band) - base level 0 cost wise
Sport Watch Space Gray - base level +1 cost wise
Watch with rubber bands - base level 0 (Watch version) cost wise
Watch with classic buckle - base level +1 (Watch version) cost wise
Watch with modern buckle - base level +2 (Watch version) cost wise
Watch with milanese loop - base level +3 (Watch version) cost wise
Watch with leather loop - base level +4 (Watch version) cost wise
Watch with link bracelet - base level +5 (Watch version) cost wise
Watch Space Grey with link bracelet - base level +6 (Watch version) cost wise
The 38 and 42mm models will have the same price. (common with swiss watch makers)
Just my 2 cents