Upshot — value-creation per head and salary level would rival the high-flying manager roles.
Imagine a highly successful trading shop. Even though the trading profit (tens of millions) is comparable to a bank trading desk with hundreds of IT head count, this trading shop’s core dev team *probably* have a few (up to a few dozen) core developers + some support teams  such as QA team, data team, operations team. In contrast, the big bank probably have hundreds of “core” developers.
 Sometimes the core teams decide to take on such “peripheral” tasks as market data processing/storage, back testing, network/server set-up if these are deemed central to their value-add.
In the extreme case, I guess a trading shop with tens of millions of profit can make do with a handful of developers. They want just a few top geeks. The resultant efficiency is staggering. I can only imagine what personal qualities they want:
* code reading — my weakness
* tools – https://bintanvictor.wordpress.com/2012/11/08/2-kinds-of-essential-developer-tools-on-wall-st-elsewhere/ * manuals — reading tons of tech info (official or community) very quickly, when a “new” system invariably behave strangely
* local system knowledge
* trouble-shooting — and systematic problem-solving. I feel this largely depends on system knowledge.
* design — it right, and able to adjust it as requirements change * architecture?
* clearly communicate design trade-offs in a difficult discussion * drive to get things done under pressure without cutting corners * teamwork — teamwork to back down when needed to implement a team decision