The extended metaphor is life can be related to someone that sells people something, and that life sells beauty. I can conclude this because in the poem, many things which are considered beautiful are up for sale.
the ocean's waves
fire (warmth and comfort)
children's faces (innocence, happiness, wonder)
pine trees scents
love (agape, eros, philia, etc.)
"holy thoughts."
Hope this helps. HAVE A BLESSED AND WONDERFUL DAY! As well as a great rest of Black History Month! :-)