Rick Segal has said that proper signage will help an item sell up to 50% more than without a sign. Here's why...
First, there is this group of people known as Introverts.
About half of your customers identify as Introverts. They tend to think to talk instead of talk to think as Extraverts would do. If they don't know an answer, they'll look first for a sign that might give them an answer before asking an associate because asking an associate puts them in an uncomfortable position.
Therefore, to make your Introverted customers feel more comfortable in your store, thus more likely to buy, give them signs that answer their basic questions and help them feel more knowledgeable. (Note: although I cannot prove it, I would be willing to bet that introverts make up a larger portion of online shoppers than extraverts.)
The second group that relies on signs is Men.
Yep, the guys shopping your store are far more likely to read signs than your women customers. Paco Underhill points this out from his own research in the book, Why We Buy (if you haven't read it, it is a MUST for retailers!).
According to Deborah Tannen, men speak vertically and women speak horizontally. When men talk they are thinking in their minds, "Did what I say make you think higher of me or lower of me?" Vertical. That is why we are so afraid of asking for directions. The three hardest words for men to say are not, "I love you." They are, "I don't know," because it makes you think lower of me.
No sign? No Sale.
When a man enters a store, the first thing he looks for is some sign telling him where to go. If he has a question, he's going to look for another sign to answer that question. No sign? No sale. Some guys will actually walk away before asking for help. My wife knows this all too well. If I come home from a store empty-handed the first thing she says is, "Did you ask someone?" (No, I probably didn't, although I'm getting better at it.)
Women, on the other hand, are thinking, "Did what I say draw me in closer or push me away?" Horizontal. They are quick to ask for directions because it brings them into the inner circle. You can put up all the signs you want but only the more introverted women will spend time reading them. They'd rather interact with someone.
50% of all the women and 100% of all the men (give or take a point or two) are looking for a sign. Are you going to give them what they want or let your competitors give it to them?
Rick is right on this one. Signs do sell!