Everyone's situation is unique. For many, it may not be easy at all—you're right. But in the "average" case of the average software engineer in the US, if you value the option to take a year off, it is absolutely trivial to save half your income.
Let's just do some back-of-napkin math to prove my point. The average American software engineer makes $110,944 / year [1]. The median salary in the US is $54,132 / year [2]. That's less than half an average software engineer. In other words, most Americans—even if they spend every penny they earn—live on less than half of what an average software engineer makes.
So yes. On average, a software engineer should be able to save half their income and take off a year. Or hell, save 33% of their income, and take a year off after working two!
[1] https://www.indeed.com/career/software-engineer/salaries
[2] https://www.firstrepublic.com/insights-education/how-much-do...