Come on, it's 2016, the female partner can take care of herself. Valiant knights are not needed anymore, she's slaying dragons too.
It's even worse than those. A luxury car will probably be high quality, and might have extra features not standard on more reasonably priced cars. Living in a certain part of town is probably safer. A fancy diamond is only expensive because people think it can be expensive.
It is like getting a luxury brand car or a watch or living in a certain part of town. All aren't practical.
When social pressure is already there, you are asking the female partner to break the norm which can be tough.