6,000 pounds seems horrifically high for that kind of trip, especially if they're telling you that they'll get you coast-to-coast in 3 weeks. Just to give you a referrence, there's a huge bike ride across Iowa every summer with roughly 20,000 riders. It takes a week doing 60-100 miles a day.
I think that you could do this on your own pretty easily if you take the time to plan it right. You can probably find some folks on this board that might even be willing to put you up for the night if you're in town.
If I were going to embark on such an adventure, here's what I would do:
- Pick a starting point - are you going east to west or west to east? Starting in New York or Miami or DC?
- Are there any places that you absolutely want to go? Yellowstone Park? The Grand Canyon? Las Vegas? San Francisco?
- Are you going to camp or stay in hotels? Camping is cheaper, but you need to figure out if you'll be cooking your own food or eating at restaurants. Will you bring a tent? If you're staying in hotels, you might want to find the AAA guide online since it's generally a good rating system for most of the cheaper motels
- Do you really want to cross the Rockies, the Appalachians and the Sierra Nevadas? Those are some pretty steep hills.
- In case you are injured or have an emergency, do you have health insurance or an emergency contact here in the States?
- Do you really want to try to bike in the big American cities like New York or LA (Chicago is actually pretty bike-friendly)?
Those are the questions that immediately spring to my mind. If the company charging you is going to make all the arrangements and be responsible for getting your bike from there to here or supplying a new bike for you, then maybe it's worth it for you, especially if they're giving you a guide too. It sounds like a fantastic trip, and I hope that you'll keep us updated if you decide to do it.