Who sets the value of your home?
The biggest nightmare for a listing agent is to walk into a home and give a presentation and when you are done and the seller is all proud and and says "well Bob from ABC Realty says my home is worth $750,000" and the Realtor looks around at the outdated 1100' square home and thinks "$450,000 tops!". Then you don't get the listing and see it pop up on the MLS with Bob at ABC for that crazy $750,000.
Now there are so many things wrong with that scenario but we see it happen over and over again. It's not just that Bob is an idiot it's that the seller has been done a major dis-service. There are many reasons Bob will do this to the seller. One is that the home is in a busy location and Bob just wants his sign in the yard as an advertisement. Hundreds of people drive by that home everyday and sees Bob sign. Free advertising for Bob.
The other reason Bob is doing this is he figures he will get the listing at a high price and then talk the sellers down later as the home sits on the market for months with no traffic or offers. Then he has the heartfelt talk with his clients and says something like "well the market has gotten softer I think we should talk about a price reduction". That is is after the seller has lost months of time and then the weaken their position by chasing the market down and basically negotiating the price down against themselves.
The moral of this story is that no one sets the value of your home except the market. The market doesn't care how much you "need" to get for home. The market doesn't care what Bob thinks he "get" for you home. The market doesn't even necessarily care what the home might appraise for. And the appraisal is another thing that might come back to bight the seller and Bob in the butt at some point. Nothing worst than a home that doesn't appraise.
What it boils down to is that the market sets the price for your home. Zillow does not, your broker does not, the buyer does not, the buyer broker does not. The only thing that sets what your home is worth is the market. If the market likes your price you will get offers, sometimes multiple offers. So if you have 3 real estate agents come out to your home and 2 tell you about the same price and another tells you 25% more than the other 2, you should be concerned about that broker.