Each of us approaches woodwork, be it a business or hobby, differently.
Long before I started buying Festools in 2006 I had owned many electric and air-powered sanders.
When I talked to my Festool dealer that first day I could see the advantage to the TS55 used on guide rails in conjunction with a CT. Once my new CT22 was set up in my condo I tried connecting it to a fairly new PC 125mm Quicksand, using a third-party paper which only lined up with a single hole. Still the dust extraction of better than I expected. Once it was too late to make sanding noise, I studied the Festool catalog. Reading that I learned that Festool sanders were different in that they blow air through the center hole and extract dust and air through the other holes. The Festool advantage is the blown air keeps the abrasive and work cooler.
This made so much sense to me that a few days later I bought an RO 150 and a bunch of Festool 150mm abrasives. Festool claims that the better cooling and extraction allows their abrasives to last longer. Frankly I had never been price conscious about sand paper. I had bought the PC Quicksand at a Lowe's and that 3rd party paper was what they had. When I bought my first RO 150 I did not even remember the price of the Lowe's 125mm paper.
Sure, when I estimate a job I include the cost of CT bags and Festool abrasives, along with blade and bit sharpening. I do still sometimes use 3rd party paper on my non-Festool sanders. Yet I have never used other brands of abrasives on my Festool sanders. Since 2006, as I added Festool sanders to my equipment I have virtually stopped using my older sanders, even the 2006 PC Quicksand.
Can I prove the increased life of Festool abrasives actually reduces my over-all cost of sanding? Frankly I have never tried to do such a calculation. During any particular sanding job abrasive paper gets changed because of a need for a different grit anyway, so the fact Festool paper might last longer does not save me much time. I am not sure sanding is only about saving some money.
Normally I am working with expensive wood. Constantly I can tell my results are superior because the work stays cool, thanks to Festool engineering. Making face frames nearly all our sanding is with Festool machines. We use a lot of glued-up panels for cabinet doors and drawer fronts. We do use Festool sanders to remove excess glue. After that we do have a wide belt sander which does an excellent job, but still there are parts of the raised panel that is better sanded by hand with the LS 130 EQ and custom pads.