Tell him the truth. "That guy came over here and asked me to give him a price because he wanted his lawn to look like this one. I gave him a price but it must have been too high because you got the job instead. There is no 'one specific thing' I do to this yard to make it look good. There are a million factors in this business and my experience tells me when to do certain things and how to react to different circumstances. You don't want to stand here while I conduct a 4-year lecture in turf maintenace do you?"