I have probably learned more about the development of new construction than I ever cared to but regardless I have made a few observations. Learn from someone else's mistakes.
Architects have no idea what it takes or what it costs to build something. Just because a room is 10 x 10 using a specific material that costs so much a square foot is not a simple calculation. The room is like a pattern. If the fabric ends up being wide or narrow the amount you need varies. Perhaps it is a fabric really hard to work with so labor goes up. All those particulars equal the cost.
This morning I had a conversation with a guy who makes cabinetry. He says he consistently sees that clients expect a certain price for a build out based on what the architect tells them it will be and it ends up 50 pct more when the bids come in. Starting the build out off on a bad foot is not fun. Then there is the scramble to get the price down. Bad subs get hired sometimes because the price is lower. Then the work is shoddy and there are no checks and balances with a fresh set of smart eyes looking at the drawings and asking questions and what is built is crap. In the end it costs money to fix it and you end up at the first price which was too high because of the way it was designed.
Everyone has a different set of skills they bring to the table. Architects can design, that's it. Contractors can build off of plans that are complete. Incomplete plans cost the client more because this is where contractors create change orders because the price was never confirmed before going to contract, there was a range. Clients rarely find out that the plans were not complete until half way into the job. Then there is no choice but to pay the cost. Architects tend to send plans that are only 80 percent done to bid. Architects truly don't care if they spend more of your money. It isn't important to them, design is.
My advice is hire someone who represents you and understands your needs such as budget, timing and "must haves". It costs money to hire an owners rep (that is what someone like this is called) but saves you money in the long run because they understand everything that I have explained above. Also do your diligence. Ask to see the full set of plans before sending them to bid. Trust your gut on price. Know what the market is paying dollars per square foot for build-outs. Talk to the contractors bidding on the job. Don't let your architect run the job.
Its your money, get involved. Even if you have done 200 projects, each project takes on a life of its own. The key is knowing what you want, setting expectations and holding tight. Otherwise you will find yourself writing checks for a lot more than you bargained for.