I agree, mcox33. They are overpriced, but how many other large volume pumps are available that have controllable variable speed electronic motors and with multi-pump control features that can produce a wide-spread softer flow at very high volumes? Some ppl can't wait for the price to go down or the company to go bankrupt from not buying.
I didn't buy these to have gadget toys in my tank. I had problems with my tank (for a long time) and water flow was one of the major contributors. Running five 1200 maxijets didn't help. Plus I had to down the number to two maxijets because of the amount of heat they produced (raised my tank temp a min of 5deg) so after much consideration and passing of time I pulled the trigger and went with the Tunze Streams. I have been very happy with the results, except for heat which is expected from anything in higher wattage that you put in your water. But the heat that one 6100 Tunze gives off (45watts) is comparable to two small 1200 maxijets (40watts) and the benefits out-weight the maxijets by far.
I guess it really depends on your individual tank requirements, amount of knowledge grasped through research and personal preferences of trying to create a more natural reef environment. And not to forget how much money your willing to throw at it.