Real estate commissions on homes in the US are typically between 5-6%. And it is usually split between the seller's agent and the buyer's agent (or it goes all to one agent in the case of dual-ended deals). It is also customary for this commission to be paid entirely by the seller (through the proceeds of their sale), though you could argue that buyers end up paying for it indirectly. All of this is generally true in Canada as well.
This is a good set up:
Sellers don't pay until they sell and have fresh cash
Money being deducted from proceeds (the "take rate") is a lot less noticeable and has a lot less friction than cash you just have to pay out
Buyers kind of don't pay
This last point is one of the most important features of how real estate commissions work. Because you have one side of the transaction that feels as if they're mostly not paying, it generally helps to perpetuate the status quo. If both sides had to directly fork out cash, you'd likely have a lot more people saying, "hey, why don't we consummate this transaction over here, on the side, and not pay these fees."
But it turns out that the US Department of Justice isn't happy about some of these policies and practices. More specifically, when the National Association of Realtors