A basic transputer was able to achieve a high number of computations per second as it wa specifically designed for parallel computational tasks. For example in image processing, the same calculation is applied to each pixel or area, which can be done in a parallel fashion. This nicely complements generic CPU's such as the 030 that was the state of the art at the time. Some boards took 8 of these transputer chips it seems.
DSP's are different but the fact that Commodore played with the idea of including it in the AA3000 shows they also investigated the option to include an extra coprocessor for specific tasks...
My question comes from curiosity. Have never seen such a board for the Amiga even though it appears there were different ones.