Remember this as you shop for must-have gadgets: You’re buying far more than a box of circuit boards when you pick up a smartphone or tablet. You’re setting path through the digital world, and turning back could be painful.

Companies are stepping up the range of content they offer exclusively to customers as a way to stand out. Apple offers a bevy of quality apps and music through its iTunes Store. Amazon touts access to its enormous online marketplace. Google offers seamless integration of mail and documents. But what people often don’t realize is that each 99 cent app or $2 song sinks them deeper into a lasting relationship with a company.