Of course they pay for it. They pay for it with time and effort. Or does the island produce fresh slave labor to pick the fruit every day also? Maybe monkey slaves?
The notion of a UBI depends is dependent on the men are willing (or able to be compelled) to accept some X amount of fruit that is less than they would otherwise get, in order to create this indemnity fund. This might be a tax (the men must give up some fruit every day) or it might simply be fruit that is collected directly by the system making less fruit available for the harvest.
Yes, you can garnish the wages of the evildoers to partially fund this, but you must first catch the evildoers (which takes resources that need to come from somewhere) and also there are some crimes that simply aren't going to get solved. You also have to make sure the system isnt gamable (fraudulent claims).
Also, different peoples' time has different value. If someone costs me one day, does he owe me what I bill out at for one day (spoiler alert -- its a lot) or what he makes in one day.