A poll on LinkedIn asking just that question got 500+ responses. Here are the results (note, the amounts are in British Pounds): While revelatory in itself, segmentation always yields additional insight. Here we see the cost per business-to-business telemarketing lead broken down by company size:

A common issue of contention arises when a marketing campaign uses multiple marketing channels: who gets credit for the conversion? This question becomes significantly more urgent when commissioned telemarketing agents are involved in the campaign. For instance, say a client were to promote a training seminar by mail, advertising, fliers, as well as commissioned telemarketers.