Why is there *such* a difference in price between new build homes and resales?

Your UK average resold property goes for £206k vs £255 for a new build.  A massive difference in my mind. 

Land Registry Prices for New Builds June 2016Land Registry Prices for New Builds June 2016

Is that because new builds are more appealing and desirable than resales?   Are they larger than the average older property?   I know that new builds have additional costs, clearing a brown field site, developer profits, S106 funding, affordable housing contributions and SIL funding to the council. 

I don’t have all the answers but it’s a sizeable difference.

My key lesson is how well presented new builds are by developers.  Does this account for a large part of the difference and how can homeowners present their homes in such a way as to overcome this?  Cleaning and dressing come to mind.