I have grown up and currently live in Sterling, VA. Here's the lowdown on the neighborhoods and the price disparity:
Sterling Park (built early 1960's) 20164- something like 4% of all homes in Sterling Park have been foreclosed upon in the last 2 years. There are many foreclosures, and the neighborhood in general is economically depressed. The homes are old and ill kept, there is no HOA, and the average income is very low compared to the rest of the county (Loudoun, the 2nd wealthiest county in the nation)
Sugarland (Built late 1960's-early 1970's)- This neighborhood is only a step above Sterling Park. Home to a large Latino community, the neighborhood has been hit hard by foreclosures and can be described in the same manner as Sterling Park. The biggest separating factor between Sugarland and Sterling Park is that things are about a decade less old and there is a HOA.
Seneca Ridge (built late 1970's and early 1980's) 20164- Just a hop, skip, and a jump away from Sugarland, this neighborhood boasts larger single family homes and older, established families. Most of these homeowners bought in when the homes were cheap, but the area doesn't have as much turnover as other areas.
Countryside (Built mid 1980's) 20165- This neighborhood has a good mix of townhomes and single family homes. Things are generally in better shape than the two aforementioned subdivisions, and the neighborhood is a much nicer place to live. Lawns are much better kept and higher income families move into this subdivision.
Potomac Lakes (Built mid 1990's) 20165- This is where a lot of the price disparity comes from. Though only a single road (route 7) separates Potomac Lakes from Sterling Park, and though Sugarland is directly on the border, walking through a Potomac Lakes neighborhood is like walking on the other side of the tracks. Things are much better kept and maintained in Potomac Lakes, and most of the homes are pretty new. They aren't luxury homes, but the county is so close to D.C. and the Dulles Technology corridor and the homes are that much better than the aforementioned neighborhoods that prices tend to be more than double in this neighborhood.
Lowes Island (built late 1990's through present) 20165-Lowes Island is home to a lush golf course and luxury condos, townhomes, and single family homes. Though I personally feel the homes are a little too cookie cutter, I wouldn't complain if I lived in one of them. They are large, new, decked out and fabulous. You will pay top dollar to live here.
Broad Run Farms (built 1960's-present) 20165-This area is unique in that it has very old homes and very new homes. The largest plots of land are available in Broad Run Farms, and a family of six in a small home with a big back yard could live next to a millionaire with a large lot full of trees and a home he had built in the last five years. The biggest reason for the high prices is that land is a scarcity in Loudoun County, and Broad Run is one of the only places left where you can purchase lots of 1+ acres.
Of course, there are other neighborhoods. There are smaller subdivisions and a 20 minute drive in any direction could put you in lower income areas than even Sterling park or million dollar homes set up cookie cutter style in the Loudoun Valley Estates. All of these neighborhoods are located under the general mailing address of Sterling, VA and are in East Loudoun County. West Loudoun County is like a whole new world. You're only a 10 minute drive from the County line bordering Fairfax, known as the wealthiest county in the nation. The lower income areas have been hit hard by foreclosures, driving the prices in the housing market down for that neighborhood significantly. The higher income areas haven't seen nearly as much foreclosure, and the non-foreclosure market doesn't have to compete with the banks.
Hope this helped.