That reminds me about windows. We built a sewing room onto the end of our house and my wife wanted one window to be as close to floor to ceiling as possible. Stock window was a 3x5. So builder and I talked about transom window above that and other options. Kind of a standard transom window would have gotten into the area above the window where the header would be (that wall supports the roof trusses) so there would have had to be something special done to allow that, etc, etc. It was going to be an extra $900-1000 just for the one window. As we were talking he says how about we go from a 3x5 to a 3x6 window. How much? <$200 extra. Sold, 3x6 will be just fine. Your project is definitely a lot larger than ours so my caution is when you ask about doing XYZ, the builder will be happy to since it is more $ for him. But many times there will be another option that can get you 85% of what you were thinking for just a small bump in cost. Appliances is another area to pay attention. We knew my wife wanted two ovens and a gas cooktop. We had had a double oven in another house and remembered the ovens were pretty small. So we looked at options w/ the appliance guy. Built-in, slide-in, wall mount, etc, etc. Why does an oven built into the wall cabinets cost 3 times what a standard one does? We ended up going w/ two standard sit on the floor between the base cabinets units. One is all electric and the other all gas and two of them cost a lot less than a wall hung double oven and a cooktop on the island.