We recently were given a small database (65K) of opt-in email addresses by a friend of ours who collects them for third parties. My boss wants to repay the favor in some way, but we have no idea how much email addresses are worth. I've always gotten my subscribers the old fashioned way, never by buying them. I realize that these kinds of lists are really only noteworthy if they're relevant to the consumer's interests in your industry and if they convert properly, but in general how much are email addresses worth?
Well, if it's a friend (who isn't looking to collect his normal fee and can wait around while you play with the list), couldn't you find some way to pay him 'truly fair' value? By this I mean: Send out a few email newsletters, with tracking code on the links, and give him 1 or 2 or 3% of the profit from the orders it generates. That way, he collects a portion of the actual value of the list he provided. I might also set a minimum value; he was nice enough to give you the list for free and it certainly took time and energy for him to compile the list even if it has no intrinsic value to you. For that, IMHO, he deserves something!