In every home purchase and home sale, it costs money; money to buy and money to sell. The listing price of the home is not the amount of money the seller will be walking away with.
When you think of net, think AFTER. Just like your paycheck, you get paid a gross amount (before taxes), but you receive (take home) a net amount. You will receive an amount after all expenses have been paid.
Every home sale is different. But some of the seller charges could include, tax service fees, maybe the title policy, compensation to Realtor(s), pro-rated taxes, courier fees, title closing fees, liens, 2nd mortgages, unpaid HOA Fees, etc.