It seems that some drawings/paintings of the castle by local artists look interesting. Am I wrong.
What to buy: Paintings.
What to pay: From approx. 10 Euros/US$ till... don't ask me. No fixed prices.
There are thousands various figures of knoghts sold in and around the castle. They are made usually from plastic but from wood and stone as well - smaller and bigger ones.
What to pay: From about 1 Euro/US$
You can buy Teutonic Knight's costume - what for? For a dancy-dress ball or... I don't know.
What to pay: From about 30 Euros/US$ till... ???
You can choose among various types of medieval knight helmets. Hmm... if you like it :-).
What to pay: From about 10 Euros/US$.