In most cases, the seller offers a commission to the listing brokerage, and the listing broker offers a portion to a buyer's broker (in this case 2.5%). The buyer's representation agreement you signed would have to stipulate what commissions are due, and if what the seller offers is not at or above that level, if you are responsible for the balance. If your representation agreement doesn't stipulate the commissions due from you, you are not obligated. Also, don't forget that commissions are only paid to the brokerage the agent works for, who then pays their agent a portion. Sellers of lower priced homes may indeed pay a higher percentage, but again, the amount and who pays the buyer's agent must be pre-defined as stated above. Good luck in your new home!