If payments are enabled in your Sharetribe marketplace, you need to define a minimum listing price—in other words, the smallest amount that an item can be purchased for.
PayPal charges a fee for each transaction, so does Stripe, and this fee always includes a fixed amount (for instance, in USD, PayPal's minimum fee is $0.30). The minimum listing price must be at least equal to PayPal's and or Stripe's minimum fee depending on if you have one or both enabled.
Additionally, if you want to define a minimum commission for your marketplace, it cannot be higher than the minimum listing price.
If you want to allow free transactions in your marketplace, take a look at Disabling Payments.
Below is a list of the allowed minimum listing price for different currencies: