I think it really depends on your hair.
For my old man, he used to get those 100NT haircuts bc he barely has any hair on his head and is the same old cut. He used to go to the 100NT haircuts, but my mother constantly told him his cuts were fugly and he ended up with the sides lopsided. He upgraded to 200NT cuts after that and had no complaints from my mom.
Myself on the other hand would go nowhere near the 100NT cuts, call me crazy, but I would not pay anything under 600NT for shampoo/cut. However, I got some circa 2012 Justin Bieber hair going on, so it takes a little more time than the normal cut, buzz and vacuum. I pay 900NT for my hairdresser near Zhong Shan MRT that I've been going to for 4 years and I'm pretty happy with it.
I've also tried QB House chain stores which charge 300NT. Most of them located in the Taipei underground malls or train stations. They were ok when I needed a quick trim, but not a full cut.