For breastfed babies, France recommend an intake of 25µg to 30µg but it's half of that in the UK (8.5 to 10µg).
It is basically wasteful, only in extreme cases you could 'overdose' vitamins.
This is not true. Vitamin D is fat-soluble, not water-soluble. Your kidneys can only filter out water-soluble vitamins. B vitamins are water-soluble; that's why there's practically no upper limit to how much you can take. Your kidneys will filter out the extra (assuming you aren't eating buckets full of the stuff).
Vitamin D toxicity occurs specifically because your body can't remove the excess vitamin D stored in your fat.
That's also why severe overdose happens over time, as opposed to instantly. You have to take a huge amount of Vitamin D at once to overdose (like millions of IUs) but you can cause toxicity using smaller doses over longer periods of time. If your body could flush it out, that wouldn't be true. Any excess would be removed and you would start each day "fresh".
Also there's some Joe Rogan-esque "just take the 5000 IU bro" even though 4000 is the recommended supplement upper bound. And devaboone warns against even using that much.