I really know about folding bikes. I suggest you try the following links:

http://www.atob.org.uk/USA_Price_Tag.html - this is a list of most folding bike makes and prices

http://www.foldbike.com

From these 2 places you will probably be able to link to all that you want to know.

I have a Brompton. I have had my Brompton for nearly 5 years in daily use especially in conjunction with public transport for commuting. I now have 3 of them and am going to buy another soon. The problem is the 4 Bromptons will be too much but I really cannot bear to part with them! However the oldest one will probably be sold when I get my new one. I will definitely get half of the new price for it as they are so popular even though it is 5 years old. I also have two normal (fullsize non-folding) bikes. The Brompton regularly comes out as the best combi on price, performance, portability, comfort, on surveys. It's not cheap but well worth it. Lots of the other folding bikes which cost a lot more, are not as good.

If you can't get a Brompton (and don't even think of looking for a used one because most people never let go of them) then the Bike Friday is probably the next best, it seems, in the USA. However the Bike Friday consistently comes out on surveys as much less comfortable than the Brompton.

Let me tell you why I like my Brompton. It folds very well to a nice compact easily-liftable and stowable package. When folded it is almost square, and there is nothing dirty on the outside. I keep one of mine in the house next to a pile of sheets and towels. They stay clean. Also when folded I have never been refused access to transport. If it rains or I am tired going home from work, I fold it and take the bus or train. If I am rich it goes with me in a taxi. It goes into the trunk of almost every car. The only hassle is constant admiring questions from people who want to know where to get one.

Also, they are much less likely to get stolen than other bikes. This is because usually you do not have to leave it on the street. It can go into almost every building with you. Mine lives under my desk when I work. I work in lots of different places and it goes with me to all of them and sits under my desk, in a corner, in a coatcupboard, etc. If you think there will ever be a problem in a building or on public transport, then to play safe you can buy a cover for it which means it is the same as a suitcase and they may not even know you have a bike inside it. Germans do this on trains because in Germany, you need to buy a ticket for a bicycle on a train and this way they can generally avoid it.

If you have any questions I look at this Board fairly regularly
Good luck
Karen