In the case of a complex contract, like the opening of a margin position or initiating the vesting contract, the amount of gas units can vary from 1,600,000 up to more than 2,100,000 gas units.
The gas fee for this transaction would be 0.06 GWEI x 2,100,000 = 126,000 GWEIs = 12,600 satoshis ~ $6.