They earn enough for average joes standard. But the amount of maintenance they'd need they'll be running on deficits pretty soon.
I dont think they can financially be independent anyway. Securities, protocols, royal shenagigans arent cheap and markel isnt a top a hollywood actress, even if she actively sought job i doubt hollywood would cast the queen of england (even if he's not the actual kings in line) in a movies where she need to show some skin, or indulge in some on screen romance.
How much does a military man make? I doubt it's that much for royals standard.