Actually...

Both such claims can easily be disproven without moving from your home.

First, some police bribing is most probably happening - but it would be extremely bad for business if the foreign tourists were themselves bribed directly. One single tourist who resists to extortion, and yes, they might be jailed - but you will also have a diplomatic incident in your hands - even Gary GLitter seems to have been more defended by the Foreign Office than he'll ever be defended by the Home Office... All bribing therefore has to be directly from brothel owners and managers to police, and is thus already built into the costs of the service and therefore paid within the regular fees you pay.

Second - compare any claim about the number with official census data and best international organisation estimates as to a) population of the places - the country and each city / town involved and b) demographic pyramids of the places. That makes every figure crumble out of sheer illogic.