Here's the breakout I would use:

Acquisition: Any work or activity focused on acquiring visitors to the site should be equated as an expense towards CAC. This includes work done by your marketing person + product development focused on your funnel and conversion points.

$40,000/year broken into small timeframes that even if performing at a loss in early months scale to profitability over time. This ties performance goals directly to the role of the employee.

Activation: Once on site, work done to activate these visitors is core product development.

Revenue: If you have a sales guy emailing leads and following up to explain benefits + convert to PU's this should contribute to CAC. The idea here is to use a direct email drip from a person and automate aspects of your drip as your acquisition funnel grows and becomes too cumbersome to manage all the individual parts.

Retention: Email triggers on auto renews, direct reach-out and support on existing customers is a direct overhead expense (cost of doing business) not CAC.

Referrals: Implementing some sort of viral hook for existing customers to refer their colleagues/friends/family is in my mind core product development and should be a value add to your acquisition strategy that grows over time.