What's an "opportunity cost"?
Imagine a youngster, involved in: Baseball, basketball, bowling, soccer, swimming. track, roller skating, violin and tennis.
It's possible to become great in everything, chances are, not really. In order to pursue greatness, one must focus on a particular skill set. For me, it was tennis.
That was actually the suggestion of my mother, who drove me and my brother to practice every single day and with carpools. She also financed my tennis lessons. Private lessons, group lessons, leagues, tournaments, rackets, strings, grips, clothes, etc. Probably could have purchased a few cars with that money.
I never won Wimbledon or the US Open. But the point is that in order to get good as something, you have to drop other things. And that's known as opportunity costs.
You can apply that to technology. I started as programmer, databases and report writing. The languages changed over time. Eventually, I dropped programming to work specifically with data.
Within data, there are a dozen different technologies to learn and master. Some people like Extract Transform and Load, others like Reports, Cubes, NoSQL, Big Data, Performance tune, Data Modeling, Architecture, Developer, Project Manager, Supervisor, Manager. And within each segment, there are a dozen different vendors and tools. And those tools must integrate with other technologies and tools.
And then we have Machine Learning, Artificial Intelligence, Internet of Things, Streaming Data, Algorithms, Statistics, Visualizations, Graph, and so on. So even within a specific segment of technology, Data, we have a couple dozen choices, vendors, roles.
You either try to keep up with all of them, become descent, or pick one or two and become great. Keep in mind, as you choose, you are dropping your expertise level on the other technologies. That is the price to pay, or cost, for your opportunity to specialize.
Or you could hit the lottery and that would take care of things just fine.
And so it goes~!