I got mine over here through a company, believe we paid about £300 or so, but can't remember exact amount soz. Elle got hers a heck of a lot faster than us tho!
Elle and I got her visa within 4 hours of applying for it.
Which I'm sure you agree was a damn good idea, without the hassle or the worry of waiting for months till they decided when you would get it. We went there and gave them all the info they needed and left Elle's passport, we were told to come back after three hours.
So in the meantime we went off to shop around Chicago, then we came back and we got Elle's passport. It was as easy as that really. It was more of hassle for Elle when she got her National Insurance number!