Is it simply speculated supply and demand, or is there a simpler approach?

This can also be done by supplying comps yourself.

Partially, to make the point that there are always those deals that do NOT fall in the realm of 'typical'.I recently rehabbed a house that I bought from a Professional Flipper who I have supplied cabinets and counter tops to (my day job) for many years.

If your talking about the Northern areas of Rockville along with Gaithersburg and Germantown I would also guess this is as simple as a supply/demand aspect.  

As with everything, pricing is based on supply and demand in the local market.

The higher number would usually be in landlord is supplying utilities.

Ideally, you are living a corporate lifestyle, where your company covers the expenses of many things for you like cell phones, gasoline, gym membership, car insurance, business trips & training, office supplies/furniture/equipment, etc.. other business expenses.

Rental units here are in short supply and renting for top dollar.Thanks again for your advice.

Keep in mind, you'll need to supply everything from plates and utensils to flat screens and art work.

You supply the land, the builder does everything else.