When couples were married after Banns being read, then their local communities had the opportunity, to object if they were aware of any lawful reason the marriage should not take place. e.g. one of the parties were already married, they were too closely related for the marriage to be legal.
Marriage by Licence could take place the same day, so one of the parties (usually the Groom) and they and a friend/ relation/employer whatever had to swear that there was no such reason that the marriage could take place.
They didn't have to pay the £200 at the time but IF, at a later date, someone came forward to say it shouldn't then they 'could' be liable to pay (or presumably be imprisoned if they couldn't pay?)
This Family Search article explains it and suggests that by the end of the 19th century the cost of a licence , including tax was £2-£3 - so maybe slightly cheaper when these two licences were issued.
https://www.familysearch.org/wiki/en/Marriage_Allegations,_Bonds_and_Licences_in_England_and_WalesI have never yet come across a case where this happened - though someone else may have.
EDITApologies, I assumed you were familiar with these licence records and didn't mention there are two pages to each one (a Licence and an Allegation/Bond) for these records. For both the links I gave, you need to also view the previous page (or next one, can't remember offhand)
Boo
