I haven't heard of any developers who make 400k. Then again, I suppose you never said this was for developers, so is there another job where this actually applies?
My last 2 job changes were in the 20 - 40K increase range.
250K is not unheard of. I guess this caps out somewhere, but if the US immigration keeps H1Bs under this control than we are going to soon experiencing 300K wages.
Do you know if it's easier to get promoted when switching jobs? I have a hard time believing that since I think you would have had to accomplish something significant on several projects to get to principal, but if you switch companies it's very hard for them to truly the impact of what you did.
When you are applying for a new, higher, role having enough experience at your current level, being sure enough of yourself and demonstrating the ability to create value within the test period will be more than enough for most companies out there.
When trying to get promoted internally you have to deal mostly with office politics. In a way, the quality of your work is only a small part. And, if you are good enough, it can go against you, I know people that have been skipped for promotions for years because their managers knew that the whole department depended on them.
Of course, there are exceptions and I admire those companies, but they are just that: Exceptions.
In SF this can be achieved quick, enough if you demonstrate your knowledge during the interview loops. For certain positions they also ask for previous experience but those positions more of the management side I think. If somebody walks in and writes good code we are willing to hire even into senior position, I don't care too much about the history. I have seen a candidate walking in to the interview from a grocery story where he worked as a cashier. Not only he got hired based on the interviews but he became one of the top performers on the team.
I think it is definitely easier to get "promoted" by changing jobs, especially if you are in a meritocratic environment, like some of the startups in SF.
The speed with while a typical ~100k dev role gets promoted or awarded payrises to become a 200k position is _much_ slower that the dev who cherry-picks better opportunities when that arise, and works out close-enough-to-truthful explanations for any resulting 6 or 12 months roles (usually with ex-colleagues who'll give references backing up your post-role-claim that it was a 6 or 12 month contract role, not a permanent position.)
Do developers in finance require any unique skills? Also is there anything special one would have to do to break into the finance industry?
There are finance startups where the above doesn't apply, but they don't pay like the banks do.
Then again, that's the only time I've ever done it, so I can't really say at all whether that trend might continue (almost certainly not).