While I most certainly have no objection to the general principle ("more skills, more better" and "he who dies with the most tools wins" being guiding principles in life) I do have to say from a mathematical perspective your statement can be questionable.I prefer to invest in myself. Imho the best way to make more money is to increase the level of my own knowledge.
Top tier skills working for the man (we will assume it is possible for the would be individual for this scenario, not everybody can learn such things and it might even be bad to try*) has a fairly solid cap in the real world (tech salaries being a massive outlier, as are a lot of financial things, collecting masters degrees and phds like pokemon cards is also not going to do much beyond maybe the second**). Might be a cool 100K USD which a nice enough life, especially with a baseline of minimalism, and rising a bit towards the end of your career for a few years if you head into manglement or become indispensable.
Assuming you keep the excess in a savings account (the money market stuff popular at the moment is a fad) vs what you would get even in a baseline index fund or other normal diversified portfolio, possibly while keeping the lesser job and paying less in.
Start heading into self employment and more active investments and it skews further still.
*see the massive gulf between smart lawyers and those that went to a bad school and squeaked past the bar exam in a lesser region. The latter could have probably done quite well in something less intense but no is going to struggle even without the debts of law school.
**there are some professional qualifications that might, some of the really high end IT stuff I saw being that, though there is also the question of whether it is that or that you had the skills to begin with.