WAY to little information to even think about a price.
REFERENCES are #1
Licensing and insurance are #1
Competence is #1
(notice a trend here?)
As far as the deck itself, what are you looking for?
Steel frame? or wood frame?
Composite (what kind? what brand?) wood? (what kind?)
Rails? (metal? composite? wood?)
Height off the ground?
Find some things you like and go from there, find a PROFESSIONAL deck builder who knows what he is doing, check out his jobsites and check for quality.
Quite often you get what you pay for, the cheapest guy might not know what he is doing or might be cutting corners. References are extremely important but they do no good if you don't call them!
I recommend that you have a design drawn up, with material fully specified (see previous post) before you begin the process of selecting a contractor. If you are not comfortable coming up with a design, you can buy a design book, hire an architect, or copy a design from a neighboring house that you like.
The discussions with potential contractors will be a lot easier for you and them if you have a detailed design in mind. Then they do not need to try to read your mind about what you really want. Mind reading is a fun parlor trick, but is almost always a very bad idea when you are trying to hire a contractor. Leads to grief and consternation, bad feelings, even broken marriages. Problem is, if you don't tell the contractor in detail what you want, they are going to bid the job the way they think it ought to go, which will never be what you had in mind. Goes downhill from there.