I own textbooks, yeah. And I use them fairly regularly too since there's quite a lot of background reading or in general stuff that they expect you to know but don't where I study, and at uni in general. It's just a fact of education that they can't teach you everything you need to know to be at the top of your field.
I don't buy them, though; most of the major ones are available somewhere online as large pdfs for free and that's something that a lot of people don't seem to know about, but it's saved me hundreds (probably thousands, thinking about it) of pounds. Just have a look around. 8)
On that note, if you were to fork out so much money for a textbook, I don't get why you'd then only read a bit of it. If you're in uni then you're choosing to study, so... shouldn't you want to use the money you're spending on your education to its full value?