Historical Import charges are based on the number of months and the number of listings for each month you'd like to import. If you would like to import any previous months of historical data for any listing that hasn't been covered by your subscription, you can easily do so, we will provide an estimate and give you the option to accept the charges. In other words, you will know always know exactly how much a Historical Import costs before you accept the charges.
When you are on a paid subscription, for any new listing you enable, you can import the current calendar month of reservations using the Historical Import feature as part of your current month's subscription. In other words, using Historical Import to pull the current month of listings should never incur any extra charges using the Historical Import feature since the charges are already added to your ongoing subscription for the month.