I don't get how people would have an issue with comparing prices. When you go shopping and look in several stores, price is usually one of the things being compared (not always the only factor, but with textbooks it's pretty important), so what is the problem with comparing the price from a store and the price online?
Shops provice a service, and have the advantage that their products are right there in front of the customers. Could you imagine an online store owner saying "I find it despicable that these stores would have books sitting right there for people to conveniently browse and buy immediately. Of course it's quicker to buy from the store, the book's right there!"
If it's all about saving money though, there are other things to take into consideration. Firstly, the time and possibly any travel expenses involved in going to a physical store simply to check their prices, and secondly, whether it's worthwhile waiting for a postal delivery of a book that could otherwise be bought right there and then. For the average paperback novel I would imagine the savings wouldn't be worth the time and effort.