If you are starting from scratch with a brand new product, you may have to guess at what the marketing cost per customer should be. For an established product, you can take historical data and arrive at acceptable marketing costs for each acquired customer. Either way the total cost of marketing involved in the acquisition of a single customer is the sum of all marketing dollars spent acquiring the customer.
Pyramid schemes - a form of multi-level marketing - involve paying commissions to distributors only for recruiting new distributors. Pyramid schemes are illegal in most states because the plans inevitably collapse when no new distributors can be recruited. When a plan collapses, most people - except those at the top of the pyramid - lose their money.
Affiliate marketing is commonly confused with referral marketing, as both forms of marketing use third parties to drive sales to the retailer. The two forms of marketing are differentiated, however, in how they drive sales, where affiliate marketing relies purely on financial motivations, while referral marketing relies more on trust and personal relationships.