The $80B in profit is a random number the OP through out.
Most likely the exchange is making between $2-$4B in profit a year (With bull markets around $12-$14B a year). However, with such a small team and the team being paid is bUSD, i suspect most of their revenue is pure profit.
Also, Binance executives are tied to Tether ($87B market cap) with around $8-12B in profit per year, and BNB ($39B market cap) $600-$800M per year, makes it one of the most profitable companies in the world.
So although $80B came from no where (And the real number is closer to around $20B a year with a market cap of $110B, $4B is nothing for them.)