Car rental companies do a pretty decent job of telling you the amount or percentage of added fees faced by renters. That's a good thing, since these extra charges often add up to a substantial amount. Rare is the hotel reservation or travel agent citing added tax percentages when reservations are made. In some cities, these amounts are proportionately astronomical. And, unless you ask specifically, you're not going to be told the hotel's policy on long distance access fees, room service surcharges and other costs that can drive your bill way beyond expectation.
Some agents are very impatient when travelers start asking specific added-cost questions.
They're under pressure to get callers on and off the phone in specified time periods. If you want a good idea of the expenses you will face, hold your ground and insist on answers to all questions pertinent to your stay. In recent years, cruise travel pricing has become much clearer with most lines now including port charges in their advertised rates. Keep in mind that this is common, but not universal. You also want to confirm tipping policies, fees for on shore activities and the cruise line's policy on charging for wine, spirits and soft drinks.