The error in your importxml was in the xpath syntax. here is the correct one:
=CONCATENATE(IMPORTXML("http://www.walmart.com/ip/Morton-Sea-Salt-Fine-Salt-17.6-oz/10849552","//*[@itemprop='price']"*[@itemprop='price'][1]"))
edited: added the [1]
at the end of the xpath to prevent the duplicate price.