There are two main ways to use MT providers' Accounts with Intento which are radically different from a billing perspective. You can run translations directly via Intento or else by connecting your Service Account set up on the MT provider's side.
In the first case (via Intento), you avoid being charged by the MT provider and hence receive invoices only from Intento. Intento, in turn, receives invoices with usage data from the MT provider.
In the second case, once you set up connected accounts in the Intento Console and authorize Intento to send translation requests on your behalf, you receive MT usage invoices directly from the MT provider.