For instance, with a Sale price of $400,000 but $5,000 paid to the buyers for closing costs, commission is normally calculated on $395,000.
Again, this can be changed and negotiated, but that seems to be common practice as the seller is really netting $5,000 less in this example.
No, it's not. It doesn't matter who pays the closing costs, the realtor's commissions are set into place the day the contract for the listing gets signed. The realtor agrees to sell the home for the seller, and the commission is decided by the seller and the realtor, and agreed upon by the seller. But that is the amount that the realtors will receive, no matter who pays the closing costs. Hope that helps!