I think something like 17,000 bitcoins worth get traded each day, not sure if 5 could be bought at the same price... But Coinbase, coinspot you have to "earn" your way to big amounts. Because it can be quite easy to do a dodgy on them with the way crypto works. So for example a mate and f mine been trading for over a year and his limit is 20,000pounds. My Coinbase limit is $500 a week. Coinspot... I dunno, $5000? I'm not sure if there's brokers around or something might be able to do big purchases. There'd have to be.