Solution 1: Buy 2'x2'x1/4" panels and put them together to form a 4'x6' board. 1/4" panels should be light enough to carry in 6 panels together, compact enough to fit in the trunk of my car, and should be cheaper than $290.
Result 1: 2'x2'x1/4" stranded/particle board is light weight, cheap (currently $1.59 a panel, pre-cut), easy to use and compact. The other nice thing is we should be able to use both sides of the board for different board terrains.
The problem that I ran into was being that the tables were 30"x8' instead of 3'x8' tables they stuck out about 9" from the table edge and were not very stable. So it wouldn't be good to play with and would require us to add another table to make it stable enough to play on. Though might work well on my dining room table as it is 40" wide, so only hanging over about 4" on either side so less likely to flip over, but where we need it the most is at the game store.