The search volume and Adwords CPC metrics are updated every 30 days after the keyword in question is added to the keywordset. The data in this case comes from keywordtool.io:

In Keywordhunter, this data comes from kwfinder.com:

Therefore, there may also be slight differences between the data in Keywordhunter and other views such as Content Pipeline. Ultimately, both providers obtain their data from Google Adwords. How often kwfinder.com updates search volume and Adwords CPC is currently unknown.