Elbox cannot make SharkPPC cards they were just rebranded Sonnet cards which are no longer made. Sonnet have sold out of all their back stock (probably to hopeful Amiga users).
The sonnet cards were on sale for under €100 for many years. If Elbox had been able to use them with their mediator hardware, and sold them for 2x price increase, they would have. I speculate a fundamental hardware problem exists and that is why we never saw anything, not even an OS'less demo.