A man is rich in proportion to the number of things he can afford to let alone.
Wealth, on this view, is measured not by what you gather but by how much you can leave untouched without feeling poorer. Thoreau flips the usual arithmetic: someone who needs a bigger house, newer gadgets and constant approval is tied to all of them, while someone who can pass them by calmly is freer. "Let alone" means doing without or leaving be, so the Turkish "görmezden gelmek" is slightly narrower than the original.
The line comes from Walden, Thoreau's account of living simply in a cabin near Concord, and it fits the Transcendentalist faith in self-reliance. It also echoes Stoic and Epicurean thought, which treat fewer wants as the surest route to independence. For Thoreau, the true cost of a thing is the life you must spend to get it.
Today, someone might stop upgrading their phone every year and silence most notifications. The money saved could shorten a working week, and the quiet gives attention back. Nothing dramatic is needed; just notice what you can comfortably leave alone.