Note a visa waiver now costs 14 USD. You also need at least 72 hours to get it so don't delay. Check the link below and learn more about your requirents.

From the official ESTA website ESTA visa waiver online

"On March 4, 2010, President Obama signed into law the Travel Promotion Act (TPA) of 2009, Pub. L. No. 111-145. The Act directs the Secretary of Homeland Security to establish a fee for the use of the ESTA system, comprised of $10.00 for each VWP applicant receiving authorization to travel to the United States and $4.00 for the processing of the ESTA application. Applicants who are denied authorization to travel to the U.S. under the VWP will only be charged $4.00."

Well we know the USA is all about the mighty dollar annoyingly. I’m only in transit! and forget telling me that it costs to process me through immigration, we do the same for your lot free. There are certain costs countries should bear (or airlines). I can't find an argument for asking the traveller to pay.