Why seller's bulk shipping cost information missing from the getTransactions call response?
For any order, if the payment for labelling is done using version 1.0, those transactions won't show up when you use the "getTransactions" call in the Finances API. This API is specifically built to work with eBay 2.0 payments (eBay-managed payments). To explain further, if you buy a label using PayPal, it's considered an eBay 1.0 payment. In eBay-managed payments, PayPal as a payment method for shipping label purchases is not supported yet.