Copy-writing on the pricing page: "We'll charge you for your traffic to FastComments. For example if you have a small blog and you never get more than 250000.00 visitors a month you won't be charged more than $71.43 a month."

Who measures number of visitors down to their 100th part? Remove the ".00" to make it simpler. The price "$71.43" suggests the underlying pricing model is somewhat complicated, as others have identified, too.