Mikhail Mikhailovitch's daughters both made matches, which if not quite royal, commanded a mixture of financial security and social status. Nadejda married the Marquess of Milford Haven, eldest son of Louis and Victoria Battenberg, thus status if not money. Anastasia married Sir Harold Wernher, who was indeed quite wealthy and lived at Luton Hoo, which I believe has some rather nice Imperial artefacts.
Mikhail's marriage was nonetheless a morganatic marriage and I am pretty sure that one of the reasons that he and his wife lived in England was because Sophie would never have been accepted by the IF back in Russia. Did the Tsar punish him in the same way that Kyrill and Ducky were punished, ie loss of rank and income?
I'm sure that I also read somewhere that after the revolution that Mikhail and his family, like so many others, were obliged to live off the proceeds of the sale of his wife's jewels; in spite of this the current Marchioness still owns a wonderful taira set with rubies and diamonds that certainly belonged to Nadejda and may have belonged to her mother.