Was Liev Schreiber the rich one ?
...or his wife ?
shareThe wife Greer was a wealthy author in her own right but I recall in episode 1 how she told her son all the “blue blood” things she tried to learn as a young woman before coming to meet the wealthy family of her future husband Tag Winbury. So I think he was the truly rich one with the inherited wealth and estate.
shareThe confounding detail is in one of the "police interview" scenes where one of the characters says that all the Winbury money is tied up in a trust and that Greer is the one bankrolling their lifestyle. Yet Will, the youngest son, tells Merritt at the beach that he's about to come into his share of the Winbury money.
Most trusts have a clause restricting access to money based on age, though often with wealth the age for getting full control of it is like 30, with the trust handing out disbursements for living expenses, school, etc, as overseen by the executor of the trust. It strikes me as unlikely Will's getting into "support young socialite and her baby with someone not Will" levels of money at age 18. It's probably more like enough money to support a cushy, entry-level-tech-bro/luxe Harvard student existence, with the bulk of the funds held back.
But even then a lot of family trusts at high levels of wealth are structured first and foremost to preserve the nest egg and hand out periodic checks based on investment performance, and nobody gets control of the whole kit and caboodle or even the ability to loophole it through influencing investment decisions. Since they said the Winbury's have owned that property for like 6 generations, my guess is the family trust is oriented towards intergenerational wealth and not some big payoff.
The trust could have shrunk enough, though, that Tag and live a very sumptuary life and the Nantucket house expenses are covered, it's not fabulous, 5th Avenue Penthouse money, either. Thomas doesn't have the cash for whatever luxe apartment his wife wants and Tag is probably cash-poor enough that he won't front the money Thomas wants for it (under the guise of an options-play investment bailout).
TL;DR -- the Winbury money isn't Rockefeller-scale, but it supports a tailored-linen-shirt wardrobe and Nantucket summer house lifestyle. Greer has to crank out bestsellers in order to live the fantasy Winbury lifestyle.