How much should it cost you to obtain each customer action using lead-generation tactics? Will the CPA be cost-effective and eventually lead to a sale?

Will the money you spend to obtain a customer action using a lead-generation tactic be more or less than the amount you will eventually make on a sale?

After performing that action, will customers make a one-time purchase from you? Or will they be a long-term customer, continuously buying additional products from you over many years?