I've kept pretty good track of my progress, riding trends, and expenses on this trip, and that data is summarized in a few representative figures here. The raw data is also available is you want to do your own analysis. Hopefully this data will be interesting in its own right as well as helpful to others who want to take similar trips in the future.
How far do you ride each day?
My average distance was 127 km/day for the entire trip, and 130km/day for the 41 days that I actually rode. For me these numbers were mostly determined by the knowing how far my total route was and knowing how many days I had to complete the trip before I had other commitments. It is probably a good idea to figure out how far you can ride and how far you enjoy riding during your training, but I didn't have enough training to do that. I found it very helpful to vary the distance I rode each day to provide short recovery days, and to make long presses on days when the weather was favorable.
How fast do you typically ride?
My speed varied a lot based on several factors. The biggest factor was wind. Next were, rain, hills, heat, and leg freshness. I basically rode as fast as I felt comfortable with given the days conditions. Only a few times did I have to go extra fast to get somewhere by a certain deadline.
Where do you stay?
As the figure shows, I stayed at a combination of campgrounds, friends' houses, and hotels. Avoid hotels whenever you can because they are expensive, and they don't provide as many opportunities to meet interesting people. Stay with friends or friends of friends as often as possible, and don't hesitate to set up a tent on the side of the road or in the desert.
How much does it cost
A lot. In my case $2724.31. Of course there are some judgment calls for what expenses count and don't count toward that total, but I think I did a good job making those calls and that is a representative total. It could be done more cheaply (see suggestions) and if I do another trip it will be.
What would you do differently?
Well, for one thing, I would take time to see more parks, monuments, and landmarks along the way, but I think I did a decent job of that anyway. But the biggest thing I would do differently is to do it more cheaply. Avoid hotels whenever you can. Buy food from grocery stores not gas stations or restaurants. Of course it feels nice to treat yourself once in a while, and I would encourage that, but remember that over six weeks that adds up. Carry gatorade powder so you don't have to spend a few dollars a day on it.
Also, spend money on quality gear up front. I bought a lot of cheap stuff which was more expensive in the long run because I ended up buying the good stuff after the cheap stuff broke anyway. Buying quality will also save you the frustration of watching your gear break as you travel or being stuck in a leaky tent one night. Specifically, buy a good bike. I had about $300 in my bike before I started and put over $700 in it along the way. If I had bought a nice bike to start with I would have spent less time in shops and had a nicer bike at the end of the trip.