It can happen when you book airline tickets, rent a car or order a taco dinner: The great deal you thought you clinched turns out to be not so great because of fees that weren’t disclosed upfront. It’s known as “drip pricing,” and regulators in the United States and abroad are trying to stamp it out. The term drip pricing has been around since at least 2009, when the British publication New Age Media used it to talk about an inquiry into online advertising, and it became more widespread in 2012,