Gacats -- I sneak those brown shopping bags in, too. But I proudly wear my LVs.
It's my money and I work hard for it. And if they think I'm being paid enough or overpaid just because I like to wear LV or other brands, well, maybe they just can't afford me anymore.
And since I'm on my soapbox, ever notice how nobody gets all in a man's business about his Armani suit or Rolex? No, it's expected that they make the money -- which is why women are underpaid at least 20% compared to their male counterparts. Ooooh, I could go on for hours but I think Susan Faludi and Barbara Ehrenreich do it a lot better.
Long story short; it's your money. Spend it proudly. And if your boss has to be a d#ck about it, find a new job.