It's not "just learning a few things". Some software engineers have years of experience on the job despite no CS education. In the end it's about how much value you bring to the company. If your diploma helps you deliver that value, great. If not, your diploma is irrelevant.

I'm always very weary of companies that tell me I'll earn more money because I have a PhD completely irrelevant to the job I'll be hired to do. It signals that they're valuing the wrong thing, and that doesn't make me want to work there.