No it isn't. For instance, in the US one starts a BS at 17-18, finishes at 21-22. Median CS PhD is in the 5-6 year range (this site, based on actual data, says 5.7: https://gradschool.duke.edu/about/statistics/computer-scienc...). So if you go straight to the PhD program (common) that puts the median finisher at 27-28.
Assume there are countries, where the usual path looks a little different. The US is not a standard for all things. In some regions you usually don't start studying at a university or institution of higher education before 18-19, a bachelor usually takes 3-4 years, leaving you at 21-23. For starting in a doctorate program, you require a master's degree (in some places this has to be in some related discipline), which again takes 1-2 years (depending on how many credits you got during the bachelor's), usually leaving you at around 23-24 before starting a PhD - at the earliest. A doctorate are 3 years minimum, more likely being around 5 years, so we're at 26-29, and this is with very little time in between to actually do anything else. Additionally, a doctorate may not enable you to get a job that pays well, but possibly do quite the opposite by leaving you on a public service salary for years, and even excluding you from certain jobs outside of academia that could be used to amortize the economical drawbacks.
