[uberalex]

I suspect $1 is too low, especially if the 6 month theory is correct. I imagine users more likely to pay 5 or 10 dollars because the perceived value of the product is higher, making it more attractive. I feel at $1 the user might think that the task offered isn't worth it.

[mootothemax]

This is it - would a user pay a "delete all your messages just this once for $1" fee, or would lump sum work instead?

I'm also wondering about maybe selling credits instead - e.g. buy 20 deletes for $9.99. My fear with credits is that it would make the tool too complex. But again - I can only try :)