If that guy had like 1000+ tokens on a sub account to spare, he just simply kept bidding on the player of the main account. By doing that, he could convert 1000+ tokens from the sub account to load of money in the main account. It's more economical than exchanging with the bank. Since after 200-300 rounds, each token may worth $3-4M which is more than the exchange rate in the bank. And the more round it goes, the more each token even worth.

Comparing to keep buying and selling free agents, it's less economical but much faster in time. If he's a rich guy, he just simply pay 100USD for that 1000+ token. If he's not, he may just farm them. I know many Vietnamese can farm like 40-50 tokens a day. Some can even farm up to 100 tokens a day. So 1000+token is not a really big deal to them.