There is a shortage for developers with certain skill sets, in certain locales, at certain prices which companies are willing to pay.

If we get away from the baggage of the word "shortage", it is a true statement that the hiring market currently favors those who are selling talent as opposed to those who wish to purchase talent, across a wide variety of first-world metropolitan areas, in many fields of software engineering, including but not limited to fairly generic web and/or application development.