Well, it is extremely difficult to come up with a fair value for DFI based on the available information on the Red Sea project. As the linked article points out the estimates about metal content and thickness of the mud in the basin comes from a German consulting company 30 years ago. One has to realise that in those days marine technologies such digital 3D seismic data, D-GPS, seafloor drills etc were science fiction, the quality and resolution of the data collected then is not comparable with that of today.
I am convinced that the value of DFI stock hinges more on HOW MUCH is there than WHAT is RECOVERABLE. Therefore, if third party funding for the DFI Red Sea project would become available, getting good geophysical and geological data for resource definition should be their main concern. Defining the thickness of the mud is most important as it likely will multiply the total value of the lease.
As for recovering the mud I am not very optimistic about DFIs capabilities. Given their poor performance in solving technological challenges in the past and their overall weak management skills I would assume that the company will eventually sell their share to one of the major companies in the field that is more experienced. For us shareholders that may not be a bad thing at all.
The current price of the stock is certainly way below true value, on the other hand $11 is far beyond what I believe is fair. My best guess would be somewhere between $0.5 and $0.7. Under optimal conditions and if there is additional money on the table to better define the resource the stock may exceed $1 a year from now.