However, after a lot of trial and error, I have come up with a workflow that combines a number of different techniques. The result is pretty good, and the time (cost) to produce images has been cut significantly and is now comparable to that of traditional photo.
The biggest benefit from using 3D instead of photo for clothing images is probably the possibility to easily try different colors, materials, prints, poses etc. It is easier to get clean images, especially if one want clothes only without a model. And the client don´t even need a physical sample of the product to start producing marketing material! Now one can launch a collection using photoreal images for the web, print, ads etc months before the first physical samples show up.
Here is a hoodie, with a pretty simple pattern, made of heavy cotton:
A slightly more complicated product with a more complex pattern, made of soft shell: