What is the maximum daily intake of BIOTIN that your body can use?

The RDA is 300 mcg but I've seen biotin supplements of doses higher than 5000 mcg..apparently from what ive heard there is no such thing as "biotin toxicity" as the excess is just metabolised and flushed out in urine..this seems like a waste to me..why take 5000 mcg when your body can only use 300 mcg? or am I getting this wrong..can the human body use up to 5000 mcg (5.0 mg!) of biotin daily?