"Silver is cheaper than the gold."
Translation:Το ασήμι είναι φθηνότερο από ότι ο χρυσός.
"Silver is cheaper than gold" I think is more normal/correct EN here as a) the sentence refers to the properties of the materials in general so the definitive article before "gold" is not needed and b) the first material "silver" is also missing an article.
Note that in GR one does the exact opposite, ie. the use of the definitive article indicates exactly a reference in general.