Can't speak to the other systems (so this doesn't really invalidate your larger point), but I have to dispel the common misconception that the Amiga was anything but profitable to the end of its days. Commodore went under due to losses from the PC clone business, and Amiga production shut down when suppliers stopped delivering parts. Near the end, Amigas shipped with dealer-installed hard-drives (paid for in cash) since HD makers were among the first to get stiffed with delinquent invoices. I would posit that, under better management, the Amiga platform could have survived and have a market position similar to the Mac today.
There is a reason Amigans are so bitter about how that went down.