In short, it s because you seem to assume that the description of the neighborhood given was also the reason why it is cheaper. (It isn't, the reason is because its way the away from the center of town with almost nothing but residential areas).
Generally stereotypes as a concept are considered inherently pejorative in the USA.
Secondly, your inference that people are avoiding the neighborhood is because of the local population. People aren't avoiding the area, the neighborhood is mostly staying the same. Large numbers of people moving into a neighborhood is the exception to the norm. Particularly in San Francisco where there are protections on existing residents such as rent control.
Thirdly, in the USA we would view asian-american as a cultural description, or nationality description, rather than as a racial description. When someone says 'asian grocery store' they don't typically mean 'because asian people shop there,' but a place where foods sold in asia are more available. This point of view would be particularly so in the bay area worldview. In the USA, it is generally considered offensive/patronizing to compliment people based on their race for any reason. People want to be recognized for their abilities on an individual level, or because of some meritocratic reason.
I could go on, but the other reasons are more or less permutations of the above.