Why is the effective rate so hard to see on a merchant statement?
Every card payment carries three layers of cost. Interchange goes to the card issuer and is set and published by the network. Visa's published table is explicit that "Merchants do not pay interchange reimbursement fees" directly; they pay a merchant discount to their own financial institution, and interchange is inside it. Network fees go to Visa or Mastercard; federal law defines a network fee as one "other than an interchange transaction fee." The rest is the processor's markup.
The FTC describes the merchant discount as the amount deducted from the transaction that "includes the interchange fee and other fees for processing the transaction." Statements rarely separate the layers. Tiered pricing folds them into qualified and non-qualified buckets, flat rates hide the mix entirely, and interchange-plus statements still bury assessments, PCI, batch, statement and regulatory line items among dozens of codes that change name from processor to processor.
So the effective rate, total fees divided by total volume, is the number most businesses cannot produce from their own statement, and the number every renegotiation depends on.