You may wish to offer a discount for buying multiple passes at once - for example, to encourage dual membership sales - which you can do by creating quantity price breaks.
Enable quantity price breaks
Create a pass bucket
From the pass bucket's General settings page, scroll down to Quantity price breaks and select the checkbox
Specify the minimum quantity necessary to trigger the price break, and what the price per pass will be when the minimum number is purchased
Click Add Another Price Break to add additional quantities and prices
Once you've added all the price breaks you want, click Save