My FIL used to have a ornamental iron business making gates/railings. Like anything you get what you pay for so shop around.
Do you have measurements ready in preparation for quotations?
It all depends on width, height, style, amount of detail ie. scrolls, baskets, etc. and how heavy you would like it making? Also, consider if you will need to have posts to fix to the wall which may add to the cost slightly. Do you want to paint them yourself, painted, galvanised?
Our estimated price for average 8ft wide gates would be approx £250-300 for a lightish pair but in our experience you would expect to pay a lot more for wooden gates especially solid wooden gates.
Personally wouldn't recommend the light gauge gates which are mass produced by such as B&Q, etc as they don't last very long and bend very easy.
Look in your Yellow pages under Architectural Metalworkers and Gates & Railings. Also, they don't make Wrought Iron gates anymore like they used to but fabricate them from mild steel.
What area are you?
Ask for references or previous work.