The most compelling reason to use email marketing is to stay top of mind with your customers. Customers rarely purchase on the first interaction. In fact, some statistics say it takes anything from 7 to 21 interactions before the customer is willing to buy from you. Email marketing helps you make those meaningful contacts in a really cost effective way. It is probably the least expensive form of marketing available. Some email marketing tools cost as low as $19 a month for a subscriber list of 500 people.