So as in title, Is it possible to buy really large BTC amounts? like a million $? What was the largest amount of BTC you bought at once?
Yes its possible to buy its not problem if you have a million $ capital and you want to buy bitcoin then gobits better to have a big capital to invest in bitcoin so that you can earn big with your profits.
I did not buy bitcoin i earn my income here and i do roll it in trading so that i increase them and store to my bitcoin wallet.