visa denied

my Fiancé ask help from a Pakistani in Vietnam for applying his visa from there. he's saying that the visa get denied once and he applied again and now he's charging him 800 dollars.. is there such thing that the visa will get denied? and then after second attempt, it became successful. its just a matter if 2 days gap. Is he just taking advantage or online visa is just like that? can it really be 800 dollars. lets say 400 dollars coz the first visa is denied. could it be really that high?