Exchange Orders can be created either with full-price items or items in the exchange order set to $0.
Generally there are two approaches we see merchants use to process exchange orders:
Refund the customer for the item(s) on the original order
Then create a Draft Exchange-Order from the Rich Returns' dashboard with the full item-price and send the invoice to the customer
Leave the original order as is
Create an Exchange-Order from the Rich-Returns dashboard with item prices set to $0 in the settings
To set this up for your process navigate to Return-Settings / Variant Exchanges and enable/disable the "Create a Free Exchange Order" option.