In a recent scenario I was working as a Buyers Agent. The sellers home was for sale by owner with assistance from an online service. This got the home on the MLS with a few photos for about $X00.00.

My buyer and it seems many others passed over the listed property because it had a lack of photos, (what's wrong on the inside?), was listed as electric heat, (most thought of a costly source of heat), not much was said about the updates on the inside over the years. There were many missed marketing opportunities as well. I could go on.

After the home sat on the market for awhile we decided to go look. 

Upon inspection, we found the home had a newly installed high efficency heat pump, (that would have added value to the home), updated plumbing, baths, other mechanicals, and a semi finished basement.

We made an offer to the sellers since they had no professional services with the listing they purchased. Seller paid an Attorney to review the offer $X00.00. No one was there to guide the seller in the potential negotiation process. Our offer was accepted and went to closing with my aid. 

In the end the seller paid a firm list the home, the poor listing and lack of proper marketing caused additional time on the market, lack of showings/offers, and a price reduction.

Costs:

Limited service for sale by owner fees.

Attorney fees.

Loss on actual market value. $x000's

Saved: 

A few grand in commission on the agreed sale price before other costs.

Are you really saving money not using a Realtor?

Other thoughts:

No secure keybox on home.

No agent to collect feedback and help with pricing and negotiation strategy.

No one on sellers side to follow up with buyers contingencies and dates.

No agent to help with repair request solutions.

Huge liability with potential disclosure issues and lack of proper paperwork.