I work for a company where our incomes and year-end bonuses are all treated as salary on the company's books. Offically there is no such thing as a binus as the year-end payment is just considered part of our salary. Lately, this company has begun to manipulate pricing of the prodcuts in our inventory so that the items in demand by our customers and the items prodcued in-house will "cost" out at artificially high prices. The official reason for this is to "force the sales staff to sell at higher prices." The real reason for this is to put the bulk of the margins into the ownerships pockets and reduce the salespersons' individual profit at the same time; thereby reducing the amount of year-end "salary" that the company will have to pay to the salesmen while maintaining comapny profits at the same time.

Is this legal?

Do you have an employment contract guaranteeing a certain amount of compensation (whatever it is called) per year? If not, then it is very unlikely what the company is doing is illegal.