I'm not familiar with "sea change" in that context. I'm not sure if this is exactly what you want to hear, but it's related... After having lived in LA, Chicago and the Bay Area I've found that by moving to southern New Mexico I can, for the same price, live in a home three times better than any in those other places. And this would be true no matter what my income level.
The internet and Adsense especially have made it unnecessary for me to be near a big city. El Paso, TX is nearby, but it's no LA. :)
So I haven't downsized but it is a "desert change..." Of all the things I miss about California though, it would be the sea that I miss the most. There are rural areas on the Pacific coast, these are looking good too.
Slightly OT: there's a new one .... "treechange". Recently in Tamworth (or Armidale - can't remember) there was a big trade show, and various State and Fed. depts, as well as LGAs, were sproiking a "treechange" to encourage more Sydneysiders, Melbourne-ites and weary city folk from down south, to the region.
Generally in the USA at least, a "sea change" is a large and fundamental change in the status quo or its underpinnings. Prohibition (and its repeal) caused a 'sea change' in the production and distribution of beer and spirits here for example. -Larry