Looking at the price gives you information

Yes, but in the cases I have in mind (e.g., buying a book) it gives very little extra information. If I've already had a good look inside a book to assess how interesting the subject matter is, how clearly things are explained, how well written the prose is, how competent the typography is, what sort of paper it's printed on, etc., knowing the price will tell me basically nothing more about how valuable the book will be to me.

I would not encourage this technique for goods whose present and future price are largely driven by scarcity and whose value to you is substantially affected by your prospects of selling them in the future. But if you're buying such goods, you should be getting scarcity information from other places besides the current asking price of the particular instance now before you.