I remember downloading the source code for HL2 (via the official SDK) and somehow I counted the lines of code and the number of programmers and the number of days it took to program and my calculations came to about 1000 lines per day per programmer. But I thought I must've made a mistake somewhere.

It's not so much the problem being simple, but more about it being a problem you have already solved. If you give me a blitter API and ask me to write a composited then yes, I can churn out the required quantity of code with ease each day. I know the problems, I know at least one solution, so I won't ever have to head up dead end alleys, stop and research options on the Internet, discover that I've chosen a really inefficient algorithm that requires a near complete rewrite to avoid, and so on. Ask me to patch an existing code base that I'm unfamiliar with to add a new option on a settings screen, and those 5 lines might take me two or more weeks to write, even though the task is simple.

More specifically Spring programmers.

<duck and cover behind my TomEE server and continues to simplify the rest of the code.>

I usually round 1000 lines of code before breakfast. At my last job, it took a team of programmer to review just half the code I was writing.