If you’re thinking about lucrative job opportunities where a PhD is required/preferred then the obvious ones would be financial “quant” jobs (usually a math or physics PhD or maybe economics) and artificial intelligence research at tech firms (usually a computer science PhD or perhaps linguistics).
Less lucrative but (to me at least) more interesting is technology R&D consulting at firms like SRI (see e.g. https://www.prnewswire.com/news-releases/sri-international-celebrates-50th-anniversary-of-the-mother-of-all-demos–and-looks-toward-the-future-of-breakthrough-innovation-in-human-computer-interaction-300760476.html).