$1200.00 to paint ALL the ceilings in white is reasonable. Do it now, not after.

Ask him to paint the ceilings in the same white as your woodwork, but in flat finish.

Then choose whatever gray you want.

BTW, what is the color of the white he is using? Not all whites work with grays. Nor do all whites look great on ceilings.

SW 7005 Pure White which is the cabinet and all trim color as well as ceilings

I personally hate "ceiling white" so if you prefer white, be sure that it is a white that looks good with your trim and wall color. Matching the crown will be the way to go. Having the ceiling in a similar but lighter color than the walls is a good look too, especially with crown molding. But, you have to just go with what you will prefer for the long term. In the context of buying a new build, is $1200 really a deal breaker?

Pure White is too gray for the ceiling with Pure White on the crown. Do the ceiling in PPG's Delicate White. Pay the $1200 for all white ceilings. All one wall color everywhere is fine for now but the longer you live in the house, you may find that you want to paint bedrooms, bathrooms, etc. different colors. If your ceilings are white, you can just paint the walls. You can get away with that with a new house for a few years.

As a rule with older homes, you always need to put a fresh coat on the ceiling the same time you paint the walls because guaranteed the freshly painted walls will make the unpainted old ceiling look like crap.

Definitely all white ceilings with gray walls or it will look too dark! That's a reasonable price too.

Just posted about this: Expert Pointers For Interior Painting

I don't think that the builder will do a % color on ceiling but I will ask.

Whenever you change the formula, you create a new color. Some color characteristics may carry over and look similar to the original color, or you could end up with a new color that looks nothing like the original color you wanted to cut. Revere Pewter is a good example. 50% Revere Pewter looks nothing like original RP; it's much grayer. Because when you cut a color's formula it's not just lightness that is changed. Hue, value and chroma all change too. Chroma especially affects how the color looks.

So, don't make the mistake of thinking you're going to get a color for the ceiling that matches or is guaranteed to harmonize with the wall color because that's not how it works. You HAVE to roll the dice, pay to have it mixed, paint a sample and see what you get.

A clean white on all the ceilings will not limit your future options as much as a color that has been somewhat grayed down. For instance, a grayed down color looks absolutely terrible next to a pastel pink or yellow in a little girls room.