Del Sur is a green community – steps were taken to make things draught tolerent, enviro friendly etc so I would suspect thats part of the higher prices.
Keep in mind that someday all that land between del sur and the new highschool will be developed. The master plan calls for shops and commercial space as well as a lot of other homes. There was supposed to be a golf course but I heard that was scrapped. If you go into Pasado, I believe they have a big land plot mockup there of the future.
From the website:
When completed, Del Sur will be one of the largest solar-powered communities in California. Water-saving measures like tank-less water heaters and weather-based irrigation will potentially save up to 40,000 gallons of water per home per year. And approximately 60% of Black Mountain Ranch’s 4,677 acres will forever remain open space for Del Sur residents to enjoy.