Seneca was a very rich man. He had nice stuff. Critics at the time, and ever since, have found this to be indisputable proof of his hypocrisy. How can a Stoic have expensive ivory tables? Isn’t it unphilosophical to have multiple houses? Or servants?
In Seneca’s view, the answer was no. Nobody said that Stoicism meant a vow of poverty, or needless deprivation. As he wrote, “Philosophy calls for plain living, not for penance...our lives should observe a happy medium between the ways of the sage and the ways of the world at large.”
Plain living is, to a certain degree, relative. A $100 steak dinner to one person is an insane luxury. To a person with a much larger salary and in a different social setting, having dinner at that same restaurant might be an unassuming and convenient choice (especially if all their friends are chasing reservations somewhere fancier and even more expensive). That Mercedes they bought with cash, that is both really safe and gets great gas mileage, might actually be plainer living than it is for the person of more modest means who is driving a brand new Nissan on a no-money-down lease (when really they ought to be taking the train).
Stoicism is not, as Seneca said, a form of self-flagellation. It’s about responsibility and sobriety. It’s possible to be sober and rich, just as it’s possible to be middle class and reckless. You only live once. Money is earned to be spent. Just make sure you’re spending it smartly and philosophically. And living, as best you can, plainly.