I would argue that a used single 120mm rad would fetch $50. Most people would rather pay $50 for a 240 rad or even some discount 360's.
And I know you can simply change fittings based on tubing ID, my point was that the MAZE and TDX blocks are old and either won't fit any current gen hardware without some customization or that they wouldn't compare to newer blocks that would perform better.
Pump, fittings and arguably the rad are what the real selling points are. What socket mounts do you have for the TDX? Is it the newer multi-core block or the older single-core block? (Pin matrix vs. wavy patterns...I still have one of the old, old single-core TDX's for socket 478.) I don't recall if they made any past Intel socket 775? (Not sure on AMD sockets)