Aren’t you the same person who tried to sell McGill’s Ultimate Back and Fitness book used on amazon for roughly double what it was being sold new?
Also, for what it’s worth, I don’t think those types of machines are worth the price. In general, for a healthy individual, e-stim machines won’t do much of anything in terms of enhancing muscle performance. For those just coming out of surgery, they can help during the initial phase to re-educate muscle firing patterns, but otherwise they have limited usage, if any at all.