Translation:The bread is cheap.
English seems much more precise, we have tons of articles and suffices to exactly describe what we mean. "Bread cheap" could mean a lot of different things in different contexts in korean, but in english "bread is cheap", "the bread here is cheap", "this bread is cheap", "that bread is cheap", mean different, specific, things - which all seem to be covered by this one ambiguated korean phrase. You would need to add more words or context to disambiguate it, which isn't tackled here yet.
Im still very new to this, but thats what im getting from these lessons and the speakers i know.
This is how it was explained to me: descriptive sentences (where you are just saying that 'X is [some adjective]') take the subject particle because an adjective can't have an object.
For example, 개는 음식을 먹습니다. <-- Dog is the topic; the object is food because the dog eats it.
On the other hand, 개가 큽니다. <-- Dog is the subject; there is no object in this sentence because the dog can't big anything.
Hope that makes sense.