Do the locations have a different value?

If the market were rising instead of falling, would you be volunteering to pay the higher price?

Does your contract have legal wiggle-room you could use to renegotiate?

Sometimes location makes a difference in price. Anything with a waterview/front is a premium. Anything closer to a culdesac is more. In some states the sun exposure i.e. SE is the most desirable.
Will those homes have as many extras/quality as yours?

Here is a simple way of evaluating your situation..If you walked away, how much would you lose in earnest money and other costs you've incurred..If that $$$ is less then the difference between walking on this and the price on the others, try to negotiate with builder, and walk away if it doesn't work and buy the other cheaper home

Just because it is the same house, doesnt necessarily mean it is coming with the same upgrades and options. Why not just ask the builder why the same home is going to be cheaper one month later, most likely there is a good explanation.