Lets put it this way, Dortmund fans are quite happy to sell Sokratis for 20m for his age 29 season. He isn't any better than Mustafi and he has no resale value. Definitely don't want, and I hope it's just more lazy rumour-mongering from the shit UK press.
Too often, we fail to factor in resale value - expensive transfer fees for young players often end up being cheap or even profitable, and inexpensive fees for older players end up being money down the drain.