video emerged showing two french tourists torching a quokka .
footage sees men laugh after igniting the creature with aerosol and lighter .
the men were given the choice of paying $ 4000 or spending a week in jail .
the pair were released from jail on thursday after choosing the latter .
the stay cost taxpayers $ 1810 a day despite them having $ 12,000 savings .
animal rights activists have said that the punishment was too lenient .