I'm not sure of the current price but yes, you do have to pay for a visa for each person travelling.
The Australian government website has sections for all types of visas, if you're going on holiday I believe it's one called an ETA. Don't bother with the various agencies who offer to "help" for a fee.
The system pairs the visa to your passport number but I'd suggest printing each completed application off as a double check.
Hope you have as great a time as we had.