Well, I created full resolution files at around 3.2 mb size, and then two Photoshop actions, bringing them first to 1000 pixels, then 750 pixels, and got finally 80 - 150 kb 750 pixel sized images that were still good to look at.
I recently delivered files to a celebrity, and she wanted them all, so I had to register them all. With Capture One 9's poor compression algorithm for smaller files sizes the file sizes would just have been too much.
Strange enough, full resolution jpegs have a great files size and quality, only if you go below full resolution the compression doesn't work - the smaller the image the worse it gets. Even 600 pixel small images cannot be made smaller than 500 kilobytes (easy to do them at 70 to 80 kb in Photoshop if you watch it and still have no quality problems).
This would be one field of improvement for C1.