Whenever I venture to the local hardware store for something costing maybe ten dollars, to my wife’s disapproval I end up spending two hundred plus on a few more things I may or may not have needed.
The first ten dollar spend (in my case) took the most effort as that is what gets me into the store, the other one ninety was easy upsell.
This is likely true for your prospects turning into customers. The first sale is often the hardest, takes the most time and costs the most to get. Once you get the customer, the profit invariably comes in the next sequence of sales.
When evaluating the return on a campaign to drive new business, consider the lifetime value of a customer and not just the first sale. In some cases it may even cost you more to get them initially.
Key is to keep them long enough for them to outspend the cost to acquire them by a factor.
Big brands know this which is why they are always marketing no matter how busy they are… do you?