My first thought looking at the new VT-12 Vocal Trainer (Roland) was that the cost was pretty steep for what I thought it was, but after having spent some significant time with it, I'd say it's worth it.
For the singer to master diaphragmatic breathing or "abdominal breathing," as well as intercostal breathing and back breathing, it is first vital to understand what the diaphragm looks like and how it functions.
I have been stung like Swift. It's never fun. But the more experience you have with it, and the less you care about what some guy thinks of your work, the more you learn to save your energy for what is important.