On a related topic, I find it disturbing that there is an IRS charge to use electronic filing, which (in theory) should save them huge amounts in labor costs.)

With credit card payments, I'm pretty sure the IRS does not allow the CC companies to charge THEM a fee (as is typical with other businesses that allow credit card payments) so the CC companies simply transfer that fee back to the consumer.

Checks will still save you money at the expense of higher labor costs which get added to the IRS budget.