Hello,
From what I read, someone who sells btc sometimes has trouble receiving the fiats in its bank account. If the sum is large, the bank turns on all its red lights. I guess it's not a problem for someone famous, but for an ordinary citizen, how it happens if he lives modestly, recovers his private keys that he lost 10 years ago and finds himself with millions?
I don't think that any person who lives in a country where Bitcoin or cryptocurrency is legal he should go through any trouble for selling bitcoins whether it is a big amount or a small amount it doesn't matter.
But it does matter, in those countries where cryptocurrency is not legalise. There you can be in danger for selling not only million of dollars or even thousands of dollars. As currently cryptocurrency is illegal in my country, trading any kind of cryptocurrency here is a punishable crime. And already many people have been caught and jailed for this cryptocurrency transaction.
So the main thing is where you are living if there cryptocurrency is illegal then 1k dollar of selling bitcoin can be a cause of trouble for you, but if you are living in a country where it is legal then i think you don't have to be worry for anything Even then, if there is any problem, it will be cleared just by showing the document.