Perhaps I'm just disillusioned and bitter.
Not all senior engineers make huge salaries. Senior engs with decades of experience at many non-tech companies might make slightly more than a junior or mid level engineer at a mid to top tier tech company. For every elite senior engineer at a competitive elite SV tech company getting 300k+ before hitting the 10 year mark, you have many senior engineers at boring non-tech companies that might be lucky to hit 200k when they retire after decades of work.
(Although it could be argued that such senior engineers are not quite as skilled or "senior" as a senior engineer at a tech company - disclaimer - I speak as a "senior engineer" at a non-tech company myself)
Also as you mention they have a really PTO generous plan. We also get several of the random bank holidays as holidays.
Another thing I like is they bought us a Linux Academy subscription, and we are given time during the day to us it. Which is nice as I like to learn new things, and this way I don't have to use my time to do it.
I actually chose this job over another that paid more because of little things like this.