Well, the price is 10-20 EUR lower. 70 EUR difference is just optical effect.
For M92 you need good cover, the screen is much more fragile and more expensive than the tablet one.
Also Booxstor explained that some cheap power sources may destroy Boox. So, you need also verified power source (if you do not use charging from PC).
Again, thing may go wrong even after one year warranty. So, 2 is better than 1.
But I agree with your opinion on marketing. It is important and Booxstor might improve this aspect of sales.