A friend recently asked my opinion about removing price tags from book covers. I have to confess that I'm a bit OC about this particular topic since I do love my books and I want them to remain pristine. First, let's ask ourselves a few questions on how important the price tags are to you as a book lover. Do you really want to be reminded of how much you've spent on to get that copy? Do you want to show your future children of the time when books were cheap? Are you just too lazy to take the price tag off? If you've answered "Yes" to any one of these questions, then don't take the price tag off.
I particularly want to keep the price tags on some of my books. I leave them on especially if (a) the books were so cheap or (b) they were too expensive. I once bought a new Jose Saramago book from National for 80 pesos and I asked the sales lady if there was a mistake. She scanned the item and it was indeed 80 pesos, so I bought it immediately. Next week, the same book was being sold for 480 pesos. This is one of the times it's good to not remove the price tag. It reminds me how someone in National screwed up.
If you do plan to take off that price tag, well then you just have to keep these things in mind. Books sold from the top three bookstores in the country -- PowerBooks, FullyBooked, and National Bookstore -- have the price tags on the back cover. This is an advantage if you botch things up. Books that have recently arrived in these bookstores have price tags that can be easily removed. Just take your time removing them, otherwise you can damage the cover. If the book has been on the shelf for quite some time, then you just have to be patient in removing it. Slowly peel off one edge a millimeter at a time. Now some price tags are actually perforated, which can make removing them even trickier. Again, in this case, patience is a virtue.
If ever you still do find some small sections of the price tag attached, you can gently scrape these pieces off with your fingernail. Don't put too much pressure though, since you're bound to make unsightly dents on the back cover if you do. Never scrape these bits and pieces off; you're bound to scratch the cover.
I also noticed that the finish of the book cover affects the way the price tag sticks to it. Price tags stuck to book covers with a matte finish are easier to remove than those on glossy book covers. Mass market paperbacks are the worst. It takes me about 10 to 15 minutes just to complete remove the price tag.
Books sold in bargain bins usually have price tags on the front cover. I just recommend not removing them at all. Since you've bought the book at a bargain bin, I'm assuming that you're not really into buying books in good condition (i.e., brand new ones). Also, I found out that the price tags used by Booksale are really sticky. When you remove them, there's a good chance of removing a small section of the front cover as well. Very, very unsightly.