A salary should not only consist of commission. It must be supplemented by a guaranteed salary on which it is possible to live tolerably. An employee should not risk their entire salary as part of the work. The employer must bear the risk of making a loss and as a reward for that he can also make a profit.
In addition, there must always be the option of receiving a higher salary and no commission, even if this salary will probably be lower than what the guaranteed salary plus commission is estimated to amount to.