I've dealt with this, I've had friends deal with this, etc. Every person I've known who shipped a car was screwed over by it. Even military people. You're lucky they told you up front that your cost was double. I had a shipper tell me that I they were doubling the fee about 45 minutes before they delivered it (I called their bluff and said I'd just report it stolen - it was an $800 rat rod Miata though).

I think the fact of the matter is, shipping cars is not going to be cost effective for an individual. Trucks are expensive, putting fuel in them is expensive, paying a trained person to drive one is expensive.

Maybe a company like Carvana could offer this as a side service, drop your car off at a local Carvana, and eventually pick it up at another location. Even then, I think the costs are going to be order of thousands of dollars.