BC Fred. I think one of the reasons the machines are less expensive is the simplicity. Compared to a Pat Trap, there are no hydraulic components (which are expensive) , no oscillation (unless you buy a Promatic wobble trap), only 1 microswitch instead of 6 or so that are on a Pat Trap. The Promatic machine frames are ruggedly built so should last forwever. The only moving part is the 12 volt motor and gear box. These are fairly substantial but should they fail, I expect $300-400 would get you replacements. We now have about 15 Promatics and have yet to have a problem once they were adjusted properly. We bought the first 3 in 2007 and have been adding ever since. Two of these were wobble machines which gives you both horizontal and vertical oscillation. The other plus is that they operate in cold weather which we can't do with our Pat Trap even with ATF in the hydraulic system. So if we want to shoot trap in cold weather we use one of the Promatic wobble machines although I am not totally happy with the way it controls randomly positioned targets.
If you want pricing, contact Tom Ferguson in Calgary at 1-800-361-1023. He is the dealer for Western Canada. He sometimes has off season specials for any stock he has left over. You can buy direct from Promatic but getting these thru Tom saves a bunch of hassle with customs, etc and you get the machines for the same price or even a bit less than you can buy them directly.
Regarding simultaneous release, if you push both buttons at the same time, they will release within a few milli-seconds of each other. I doubt whether any shooter could tell that these were not simultaneous.
Don't wire the two control cables together if you want simultaneous release as this could cause a short circuit between the two batteries. If you want to use a single switch, buy a double-pole, single-throw pushbutton switch which should be available at any automotive place like Napa or and electronics store.