Exactly. You can find many auctions on eBay with Media100 boards for sale but without its own serial number they are useless, the top system was the XR version with the highest bandwidth in capture and a separate board for realtime FX, but again the software is the less important part, the serial number is, because it activates the card and the purchased options.
I own a working Media100 XS system, a middle range model, equipped with Sony firewire decoder card and a valid 6.0 license, I admit I have only a collector's interest in them so I really never used for produce anything.
I also own an AVID ABVB system with 3D FX board (Elite license, almost all the top available options are activated) that was dismissed from a local broadcast TV station and I purchased it for a 150 euros complete with SCSI drives, manuals, original box and cables and most important, the ADB dongle to activate the license: without it the only working part would be the PowerMac 9600 that host the cards. The various board inside are connected together with a flat cable that completely bypass the slow PCI bus and generates so much heat that a large dedicated fan is put by AVID above the cards to cool them.
I believe at the time the whole system would cost over $25.000 but the target was the broadcast world, while the Media100 was more open to semipro and advanced users too.
A thing to keep in mind when you deal with broadcast equipment is that a machine like that is all but user friendly: the typical user is a professional with a specific knowledge of broadcast world and without a basis it can be tricky to understand how things are done or what steps are needed to do a specific action. I found for example the AVID environment really strange for a newbie like me while the Media100 was much more intuitive, however both workstation have been purchased for collection purposes only, I did not spent much time in trying to do something useful on them :-)
When I compare that heavy and costly equipment with modern video workstation I see an abyss of differences: the PowerMacs were almost the backbone that host a dedicated boardset, they provided only the graphical interface for the operator and a minimal I/O to drive the workflow in a direction instead of another but all the hard work were done by the AVID and Media100 boards, the most powerful PowerMac available at the time would not nearly capable of doing alone a demanding task like realtime video editing.
During the time the processing power of CPU (now assisted by GPU too) is increased so much that a video stream can be handled and manipulated without problems from a middle-class system, only an I/O box is needed but there's a trick... you can do realtime until you are editing an uncompressed stream, if a particular format is needed in input or output the power of CPU collapse because compressed formats are really an intensive task so if you don't want to loose the performance you must have a board that do all the dirty work of compressing/decompressing for you and this is the reason because the professional video boards are not simply a bunch of ADC and DAC but integrates also DSP and local memory, leaving the computer CPU free to apply the effects and doing a snappier workflow.
Another thing I have noticed during the time is that dedicated systems are progressively disappeared: while in the past every boardset had its own dedicated editing software and projects were not interchangeable between various platforms, now we have a wider choice of many hardware I/O boards that can be driven by different systems.
The Media100 Suite and Apple Final Cut for example can operate with many hardware brands without any license restrictions, you can also choose to have different suites on the same computer that uses the same board. We now have a freedom of choice as never happened in the past and a superb quality at affordable prices, the software rules and hardware is running faster and faster to satisfy its wills, this reminds me Microsoft, I don't know why... :-)
