I have the same logic; I really wanted to add another Marolex Industry Ergo to my original order of the Axel 2000, simply because I will save money in shipping in the future, because I really would like to add another Industry Ergo. But I had to tell myself no as the total was more than I was comfortable spending, so I just got the Axel 2000.
@Coatings=crack, I recently ran some numbers and by switching completely over to Rinseless/Waterless with FROTHe by cutting out the coin-op for three out of four washes, I could save about $3/wash. Over the course of a year that is at least $108 in savings. I did just order a Marolex Axel 2000, intuition tells me that I will be able to get more mileage out of FROTHe. Going from dilution of 1:20 in the Aerator to maybe 1:38 to 1:50 in the Marolex. I will report back with the findings.