Time investment, as in your own time actively doing stuff.
If it takes you an hour or half-hour of going back-and-forth to make a teleport pipe work efficiently, then I'd say it's balanced.
Yes, Chunk Loaders do make Solar Panels OP. But that's a different sort of time.
Thaumcraft is not OP, because you have to spend sooooo much time doing all the stuff. Even though you can transmute ores and such.
And that I would agree with.
But sadly a lot of the Time Investment costed base systems can be setup and just let run creating a large amount of pay out for your 'spent time' when all you really did was build it once and walk away. No up keep No additional input and in many cases can be fully automated.