When choosing a maximum cost per click (max. CPC) bid, you should consider the amount you make from a purchase because you want to set a bid amount that’s:

When choosing a maximum cost per click (max. CPC) bid, you should consider the amount you make from a purchase because you want to set a bid amount that’s:

  • The same amount as the profit generated by your product
  • The same amount as the revenue generated by your product
  • Based on how much your product is worth
  • 50% of how much your product is worth.

Answer : Based on how much your product is worth

Source: https://support.google.com/adwords/answer/2471184?hl=en