I'm not sure where you are or how old you are but after 10-20 years this definitely does not hold. Often you'll have to take a pay cut to get good skills.
I noticed a positive correlation between salary and skills. The higher the pay, the more I learnt on the job.
But maybe I was just lucky to pick Python before it was cool and just ride the wave.
I took a massive pay cut when I stopped freelancing and started a product company instead, but it was totally worth it in the long run.
Make sure you take a pay cut for the right reasons, and for the right amount.