that's very expensive for you. Maybe you need to ration it out. E.g do you buy fruit for two days? Do you buy fruit for the week?
Whatever you do, dole it out in airtight containers (7) so that each day, you can clearly say to the kids "this is the box for today - when it's gone, that is it".
That way, you will have enough fruit for the rest of the week.

i can see your bind. You want to not replicate your childhood, but you (like your mum) are not made of money.
I thought my mum was a meany for never buying real oj, just the fake oj that is really cordial. Now i understand, her priority was to pay off the mortgage fast, pay for three children's needs. Just as i have priorities too. And now as an adult (and a parent) i understand, eating the whole orange is better for me, than guzzling OJ. but i digress.

Children need to learn the value of money.
As much as you love them, you cannot afford to buy that much fruit so often.
They need to learn other options for snacks and to have boundaries around how much fruit they consume.
In the real world, they can't have infinite everything.
you're not a mean mum if you provide some limits.

It's wonderful that they are so into fruit, but not realistic (unless you win Lotto) to sustain that habit.

Do you grow any fruit? Could you interest them in growing fruit? a longterm partial solution maybe?