I used to have to temporarily import what was then high-tech equipment into third-world countries and then, unlike the UK, bribery was rampant and impossible to avoid. I tried not to pay, but I paid a bribe to get a bond back in Egypt once - it was £50 or so, or lose around £1000 for sure (which would doubtless have been shared between the bank and customs officials concerned). On the other hand I remember bringing a removable disk drive, when they were the size of a car hubcap, into Colombia. The customs officer was clearly looking for a bribe - she'd taken one off the passenger in front of me - but by spilling the rest of my suitcase contents over the floor and generally acting like a gormless wally, she soon lost interest.
Most interesting example I saw was in my hippy traveller days, crossing from Pakistan to India. A pair of Germans were caught with dope (bringing dope into India ffs - talk about coals to Newcastle). Anyway,one of them panicked and brought out a big fistful of dollars as a bribe. The customs guy said "No, that's far too much" and kept just $20.
Incidentally in Rawlpindi I could not find a cheap hotel room. After being turned down about a dozen times, I asked a hotel owner who spoke decent English what was going on. He explained that they had to register me with the local police, which involved a high "fee", the police claiming that the hotelier would charge double to foreigners. This meant that the hotelier would make a loss on the room at the published rate and so the easiest thing was to say "no". Realising I would never get a room otherwise and the Sheraton was not an option on my budget, I asked the guy what he would have to pay and got him to add it on to the room price.