Let me add: If you want a quote to get new spark plugs installed, or new brake pads installed on your car, you already know what service needs completed, which is why you can get a solid quote. In this case, Festool isn't entirely sure of the repair that your Domino needs, just the symptoms of the issue (cutting off center). So of course they can't give you a quote or a ballpark answer on cost, they don't know what all will need repaired or replaced.
I had a car a few years ago that I ended up taking to the junk yard because it wouldn't stay running as soon as you actually tried to give it gas. The power would cut off along with the engine. It wasn't the battery, it wasn't the alternator, and we replaced the fuel pump and it still had this issue. If I had called any mechanic worth their salt and asked for a quote to fix this issue, they all would have likely laughed and explained they don't know what's wrong, or how long it will take to figure out what's wrong, and how much whatever the fix would cost, or if it's even fixable. There are a bunch of different things that could lead to my car shutting off and the engine dying, so it would be irresponsible to quote me a price to fix it. This is the same as your issue with your Domino. There could be a number of things causing your Domino to cut off center and they don't know which one it is. Calling Festool "shady" for what seems like a reasonable response to your inquiry is unfair, in my opinion.