Currently, Google Pay is free whether you are a business or a consumer when using a bank, so there are no added fees.
However, when you use a credit card there are fees associated with the purchase.
Customers will pay a 2.9% fee when they use a credit card linked to the apps.
If the purchase is in store, the credit card provider might look at it as a card-present transaction. And this means they can charge the merchant a fee of up to 4%.
The merchant might pass the fees on to the customer. As a merchant make sure to inform your customers of all fees. And if you are a customer ask about any fees before making the purchase.