Sellers used to pay the commission for the buyer's agents. Since a big lawsuit last year, that's no longer the case. Now the buyer's are responsible for paying their own agent's commission. Sellers may or may not pay all or part of it. Before August, I could look at a house on the MLS, say 123 Main St, Anytown USA, and there was a line on the MLS that told what commission was being offered by the seller. So, I knew what I would be paid if I repped a buyer on that particular house. Now, it's up to me and my buyer to determine what commission he's willing to pay, and I am willing to accept.
From a practical standpoint, the seller now receives an offer, and another form (the name varies per state) which says if the buyer is asking the seller to pay the buyer agent's commission.
So, with my clients, I simply show them a "net sheet". Buyer A is offering X and asking for you to pay for title, escrow, and commission and you will net Y after all of that.
The seller can choose the offer that puts the most cash in their pocket at the end of the day.