They are the same thing.

Twist drill bits CUT a hole in the material being drilled, like aluminum, steel or wood. Masonry bits or hammer drill bits BATTER a hole in the material being drilled. That's why a "dull" masonry bit works nearly as well as a brand new one. A dull twist drill bit no longer cuts well, but a dull masonry bit bashes masonry into dust just as well when it's dull as it does when it's new.

Cost is not always indicitive of quality. The tungsten carbide at the front of the bit comes in different hardnesses and you pay more for harder tungsten carbide. You'll find that retail stores tend to charge more because each and everything they sell is vaccuum sealed onto a card, and you're paying mostly for the packaging. Phone around to see who sells these bits "in bulk", where you buy the bits loose with no individual packaging and you should get a much better price on each one.