To me, processing and lenses are about equal in importance. With proper processing, you can put your personal fingerprint on your images. You might want to have your images appear super crisp, or vibrant, or high contrast, or low contrast, or black and white, or maybe that faded film-emulation look that's oh-so popular, etc.... In the processing stage, you can take images from good to amazing. For me, this is where my images really pop. I personally have some default presets that are applied to my images upon import. I love watching the import process to see the preset get applied. The images first come in as a flat, dull image. Then a few seconds later, when the preset is applied I see the image come alive with vibrance, contrast, sharpness, and many of the other characteristics I set in my presets.
Another benefit about processing is the ability to fix mistakes. I know, I know, All photographers aim to get the exposure right in-camera (and if not, they should). But let's face it, sometimes we just don't nail the exposure the way we intended. Maybe we saw the perfect moment right in front of us with only enough time to lift the camera on the existing settings and snap a photo. Or maybe we accidentally had the ISO set on the wrong value (oops). Whatever the case, it happens to the best of us. And in that instance, sometimes we wind up with a photo that we absolutely love, but horribly under or overexposed. Luckily, with today's powerful camera sensors and a RAW file format, we can do a pretty nice job recovering photos in post processing.
You'll be happy to know that processing is one of the cheaper components, in terms of money. In fact, you can subscribe the the top image editing software in the world for $9.99 per month. That said, it's definitely not cheap in terms of time. It takes a lot of time and effort to become good at processing photos. More on this later (hint hint, that skill part I mentioned).