Monte Vista, as you know, is San Antonio's second most historical subdivision, with King William being the first. Many Monte Vista homes date from before the beginning of the 20th century. They were initially designed with no ac no heating and no electric. Because they were mansions, they were improved and renovated but many factors go into your question. Really cost per square foot is not a good measure here because of the total cost for bringing the home to a standard.
I grew up in Monte Vista in the 1950's so I love this are very much, but really purchasing here is really a function of your objectives more than modern analysis tools.