This is capitalism in action folks.
She found a niche, worked it and has made huge $$$$. Say what you will, the Wheel of Foftune brand has been valuable and she is part of it, along with Pat Sajak. Unlike, say, the Kartrashian clan, Vanna is part of a legit TV brand that has spanned 40 years and is not trash.
The brand will most likely have the same fate as Jeopardy or The Price us Right when those two retire. The main demographic that watches game shows is old and will die off, leaving little to no viewers left. You also have iconic hosts that make the show, which further weakens the brand.
Unless they can make it relevant again, of course. Sajak’s daughter in Vanna’s place(or as the host maybe?) works not only in the looks department, it also is the connection to the most famous host of the show. They just need to find the right people and approach to market it to a younger generation m.