Sepp hasn't covered what his losses are in the winter that I have heard but I imagine that there is not much loss at all. Colonies are allowed to keep their honey to get them through the winter and with the thick log hives they have good insulation for the winter that is still breathable. The bees are allowed to build their own comb, leading to them selecting the size for future bees. This helps reduce the effect that Verroa mites have as the smaller bees are often able to pick the mites off of their backs. The bees live quite a natural life with very little stress, stress is the root of all diseases.
They certainly do sell honey at the Krameterhof as part of their store as people finish tours. I believe the honey sells for 5-6 Euros for a small jar. Here is a photo of one of the hives at the Krameterhof located under the eaves of the little shop towards the entrance of the farm.
Tim have you seen the thread on the log hive we made in Austria? You can see it here.