What is meant by “no transaction costs”?

This is another gimmick by the processing companies. Every card has an
assessed transaction cost. It does not matter what type of card it is and
that includes debit.
There are many different terms of “transaction costs”. Such as,
authorizations, p.o.s. costs, item costs, item charges, settlement costs,
etc.
When a processing company says they do not charge “transaction costs” and
on your statement there is a line item fee labelled item charges,
authorizations, item costs, etc. It is the same thing as a transaction
cost.