150 is definitely a bit excessive but it's still cool to have. This is definitely a well loved instrument and didn't even realize the bass buttons used to be colored black and white until I looked at the picture.Nice! Looks like a quality box. The Tula factory still offers high-quality instruments, when you pay a premium, on top of their regular lines.
First time I see a Bayan with 150 bass buttons. Most have 100. Have fun!