[RoboMom]

I assisted a team with planning a trip to the Championship on a shoestring last year.
They rented a bus and saved on two nights hotel by sleeping/traveling on Wed. night (12 hours with a stop for breakfast) and Sat. night (leaving after the wrap party). Coach buses are not cheap, but it was more affordable because of saving on the hotels. Although not my idea of a good time, they said it was fine, unlike Bharat's experience. The trip, for about 25 worked out to be about $400/pp, including bus, 2 nights hotel (booked outside the THS system, free breakfast), wrap party, vex party, and money for other meals.

Many school systems have an approved bus company list you have to use.

Lots of teams are restricted not only by money, but by time missed from school. Having a bus gives you a little more flexibility.
In 2002, before I got involved in helping plan travel, a travel agent booked us on a flight that had to change planes. Although there were about 10 non-stop flights, changing planes turned the trip into an all day thing.

My advice would be to start investigating the options now, looking at not just bus vs. plane, but with hotel, food, etc. The NEMO forums have some helpful hints.