wow, I bow before thee
The apartment complex was constructed in 1993 and has not been renovated since. That could explain the low taxable value.
My place is much older but the taxable value (in percentage) much higher. Maybe is a cantonal difference?
I experienced once that the tax value was revised after I purchased an appartement, increasing from the previous lower value to about 80% of my purchasing price.
I heard (but cannot confirm) that it is the standard practice in this canton (VD); this is beneficial for the canton when real estate prices generally increase…
For most cantons, purchase price or market value are irrelevant in the deemed rental income determination.
Instead, insurance value or specific forms are used. Each canton has its own method.
SFTA published an interesting recap on the topic in FR, DE and IT.