Probability of positive ROI on direct mail spend?

Hello guys,

After lurking around the forum for a while, I finally signed up. This is my first post!

So many knowledgeable and helpful people post here. I've learned a lot just by reading (and reading, and reading...)

I wanted to post because this question has really been bugging me:

What is the probability of achieving a positive ROI on one's direct mail spend?

In some of the forum discussions I've read and podcasts I've listened to, the likelihood of achieving a positive ROI isn't mentioned at all. The mechanical aspects of targeting prospects and running a campaign are discussed, tips and tricks, etc. But it's as if a positive ROI is simply a given.

Then, on the other hand, I read posts by other members who aren't getting anywhere with direct mail. In one post I read recently, the member was sending 4,000 pieces of mail a month and struggling to find one deal. 4,000 pieces a month!

Can you help me reconcile what seem like wildly different results between the former group and the latter? Just how likely is it that a well-targeted, persistent direct mail campaign will pay off with a worthwhile number of good deals?

Thanks!