The seller could be saving several thousand dollars by not using a Realtor. That is a fact.
However, using a person trained in the procedures to guide the transaction to closing is a best practice, since it minimizes the occurrence of errors and misunderstandings. Those can be more costly than having untrained people try to avoid paying for assistance.
If the property is not listed, then you can choose to have a Realtor represent you without having the seller pay for it. You, as buyer, can negotiate with your Realtor a reasonable fee that you alone will pay.
If, on the other hand, the property is listed, then the seller won't be saving a dime because listings in MLS contain a co-brokerage fee the listing broker offers to other brokers to bring a buyer like you.