Not coast-to-coast, but I had a miata shipped from Georgia to Texas a
while back and even that distance is expensive. This one did not run and
required additional winching fees, but even if it had run the cost was
higher than I expected it to be.

Research the company that you are using and try to talk to others that
have used them if possible. You can probably beat $1000.00 on shipping
costs, but it will most likely be a switchoff system where your car is
actually hauled by multiple trucks rather than one long trip. This can
result in your car being moved on and off the car carrier many times,
especially since they may need to roll it off just to get to other cars.
  Definitely check into what insurance they offer, if it adds
additional cost, and if your own insurance will cover damage or loss for
anything bad that may happen in transit.

Almost all of the shipping companies used contract drivers rather than
their own employees, which I assume is fairly normal for this business.

When I was researching having it shipped, there were many horror stories
of people having their cars damaged or even temporarily lost during
transit. There were also stories  of cars showing up with missing
stereos, etc., but we got our's with no problems or missing items.

I can give you the name of the company we used, but I am not sure if
they do coast to coast hauling.

One more factor to consider is that the car will need to meet California
emissions quickly after it arrives. I am not sure what is required to
bring the car up to CA requirements, but there will be some additional
expense there as well. That would be good to look into, as it may be
quite expensive. There is probably someone here who has taken a miata to
California and dealt with this.

Just send me a plane ticket and give me a little gas money when I get
there and I'll drive it across the country for you. Of course, I might
have to take a detour by Deal's Gap on the way. :-)

Pat