The cost of running a TM, even something as powerful as the 875 is a mere 4% and yet the productivity is double / treble and more what a portable can do. A dining chair takes 1.5 minutes with a TM and 2.5 with a portable, that's without factoring in all the stops for emptying and refilling, so the cost of running the TM is actually peanuts in comparison to how much it is earning. You could ask yourself, 'Can I afford not to have a TM?'
Simon