How much do you charge for extra PM storage?

[jilly]

i.e. if you were going to sell PM storage to your users, in increments of 250, how much do you charge per 250?

i.e.

250 PMs - $10 a year
500 PMs - $15 a year
750 PMs - $20 a year

etc

I know on larger boards this can add up quickly...

[aycan555]

It depends how populer is your forum :D

[alexi]

I was just noticing today that we have over a million PM's stored!