at a premium vs valuable

at a premium

prep
  • At a high, or higher than expected, price. 

  • Scarce, in short supply. 

  • Above par value. 

valuable

noun
  • A personal possession such as jewellery, of relatively great monetary value. 

adj
  • Having a great value. 

  • Estimable; deserving esteem. 

How often have the words at a premium and valuable occurred in a corpus of books? (source: Google Ngram Viewer )