The German word for sausage is "wurst." And the sausages come in many different types: They have frankfurters, bratwurst, rindswurst, blargenwurst, knackwurst, and bockwurst.
PriceThe price is right, you can buy a sausage from a food stall for appx. €2.
PhotosHere's a collection of photos from Flickr who documents the sausage life in Berlin:

Enjoy an uncomplicated curry wurst with ketchup. Tasty!

Preparing the wursts.

There's also a chain of stors with the name Wurst :-)

You never have to walk far to get yourself a sausage.

Make a meal out of it. This is curry wurst with bread and fries.

The trays of cooking curry wurst at Berlin's Curry 36 at the corner of Mehringdamm and Gneisenaustrasse.

Yes, it's really popular.

The wurst meal can be very uncomplicated. It's honest food that is tasty and OK, without the need for a lot of garnish.
I hope this was interesting! Remember to try some wursts during your trip to Berlin. It's tasty and cheap. Have a nice one!