you have no clue what you're talking about.
direct mail is one of the cheapest sources of advertising there is, and been proven to work for decades. a large part depends on what type of business you're in of course. but there are a million different variables that determine whether a campaign will be successful or not
granted, the response rate is typically less than 1% but your cost per lead (i said lead, not prospect) is MUCH less than other marketing avenues