Tamara Myers thought that her hotel bill at the Westgate Las Vegas Resort & Casino would come to $415. At least that's what Otel.com, the website through which she booked the room, promised her. But the site glossed over a small detail: a mandatory daily "resort fee" payable at checkout, which added $306 to the folio. Gotcha. "I did my due diligence," insists Myers, who lives in Indianapolis and works for the military. She'd made the reservation for her 88-year-old mother, who was caring for her brother in Las Vegas. "The fee was listed nowhere on Otel.com."Mandatory resort fees, tacked onto a hotel bill after an initial price quote - and sometimes even later, as with Myers - are on the rise again. A total of 1,026 domestic hotels charged a resort fee for the first half of 2017, a 14 percent increase from just six months ago, according to new research from Resortfeechecker.com, a site that allows travelers to look up resort fees at hotels worldwide. The average resort fee, which covers everything from "free" WiFi to access to exercise facilities, now stands at almost $21, a jump of 8.7 percent from last December.