It would not take much modification in order to get the challenge to include a paypal payment and incorporate that into the confirmation process. But I'm not going to do that. Right now, I'm imposing other costs that, to me, seem to be the right price. In order to get into my mailbox you must meet any of the following "costs":
- your email address must already be known to me, or
- you must have a working email address and respond to my challenges, or
- you must be replying to an email that I sent you within 7 days of my sending it.
For what it's worth, there is a group of people who revile C/R email systems. They say things like: "If I ever get an email challenge from someone, I will never respond to it, and then that person will never get any email from me." I've always argued with those people that it's their loss. They're the ones who wanted to send me the email in the first place, so they're the one's who (in effect) censor themselves.
However, the fact that I'm not willing to charge money to unknown users suggests to me that I'm not willing to lose email from those users. My behavior, as opposed to my statements, may in fact indicate that I do actually want to get email from them, and I do lose something.
Or maybe an alternative explanation is that I think monetary costs are too high for the "customer base" that I actually want to serve. And since that cost is effectively filtering out the customer base I don't want to serve, I've got my price set correctly.