What everyone has said so far does hold true. However, your second sentence in your question is what I have grave concerns with. "...agent who advised not to negotiate the asking price as it's not common for new constructions." I live and work in Bothell and that is absolutely garbage. Actually, it doesn't matter where I live and work...that statement from your agent is still total garbage! I have sold many new constructions and the ability to negotiate with the builder is a function of market conditions. 2 or 3 years ago when things were hot, the builder wouldn't bother to look at your offer if it wasn't full price because chances were, another buyer would come in really soon with a full price offer. However, this is 2008!!! ...the Bothell market is INUNDATED with new construction inventory and builders reallllly need to sell. This is the PERFECT market to wheel and deal and for your agent to advise you not to because it's not common practice was BAD advice. Rather than have your best interests at hand, they gave you advice that made their job easier and helped the builder out...and not helping you...their client...out. Regardless of what other people paid in the same development, this agent clearly either doesn't know what they are talking about or they're not really working for you. ...are they by chance the site agent?
Now... before you go and chew anybody out over this ... make sure your are comparing apples to apples when you compare your sale price to others...and that's where the other people's posts come into play. Is your place more upgraded than others? Better lot? etc. If not... make sure your data is accurate about what others paid for their house. ...if the house has already closed and you're basing it on public records ...then okay..you got a legitimate beef.
What contingencies do you have in place in your contract? If you find that you did severely overpay, you can see if you can get out based on one of your contingencies. Not sure how willing a builder would be in this market, but many builders would rather let a buyer go with no penalty if the buyer really wants out. This is when you need your agent to be at their best to talk their way out of the deal with no penalties. Don't know if your agent can do that based on the advice they gave you prior to writing the deal. Won't hurt trying though.
As for getting a true and honest opinion on price, if you tell us the specifics of what you bought and where, someone can probably look up all the past sales in the development and surrounding areas to give you a better idea. If you don't feel like posting that publicly, email me with the specifics and I'll see what I can find. Appraiser can do the trick as well, but that will cost you a few hundred bucks....