Does anyone have any experience with using these to create a room below the garage? I have received an estimate from a local builder. About 4500 for a 2 car garage. Does this sound right?

Bare with me now,
Are you asking about creating a room under an existing garage?
If so, I think 4500 is too low, I would charge more than that, just being honest. There are a lot of structural and engineering considerations to take into account, such as supporting the structure as it is excavated from the sides and below. Then building the foundation walls with a ceiling system that will support the garage floor overhead and successfully transfer the building load.
Now if you want to do it as new construction, the lite form system is adequate as far as the foundation goes, but pilasters will have to be installed to help transfer the load and to possibly provide support for steel beams to support the garage floor and vehicles etc.

Think twice. Such a room below a garage will certainly be more expensive than just adding a room on the ground. But if you insist, there are several ways to do it, all requiring serious engineering and VERY careful attention to detail when constructing.

I have an unfinished room (part of my basement)set up as a workshop that is below the garage.

I just wanted to see if there are any other homes with a room below the garage as I am now having problems keeping the moisture (from melting snow) from seeping through the garage floor to the room below.

The garage floor does have some sort of a coating over it which was done way before I purchased the house, but the coating on some parts of the floor is deteriorating and it is through these deteriorated areas that the water/moisture is seeping through to the room below.