commercial office space

[Konstantin Komkov]

Hello, I am new to commercial side of real estate. I am looking at how commercial office space is appraised. There are around 50 similar commercial office spaces, when they were build in 1990's they all were sold at approximately $120 per square foot. But recently they were sold at a very different prices per square foot. Some are really 1.5 times more than the others. My question is how it could be explained? From the outside they all look the same, but different square footage of cause.
Thank you ! K