You might want to check out you local welding fabricator, maybe the prices won't be too much and you can have everything custom made to your spec. You can get the square steel tube you need for just over $100 at a steel mill and my frame took exactly two hours to make, at $100 per hour that's $200 (just tossing a number out)
Next would be a totally custom torsion axle for $175 from Redneck trailer and automotive style wheels and tires for another $300 (I got 14" chrome smoothies, much nicer). I am not using standard trailer lights so those would have been tossed anyway. Oh and a $15 hitch and $15 wheel stand rounds it out at $800.
That's $200 more than the car hauler before they charge you freight and top of the line quality and custom all the way around. Not to mention you wouldn't need to bolt together a trailer, and mess with relocating axles. I know it's a little more complicated, but just another thought to ponder.
To answer your original question those numbers sound just fine!