Not the cheapest thing around for sure, but Band in a Box can provide some pretty decent fiddle, steel and banjo.
Go to my web site, and listen to some of the music there. The fiddle, steel, banjo and dobro in the various songs are BB. The downside to BB is that you can not get it to play a precise melody line, but if you take your time, use a few tricks and are determined enough, you can often get it to give you a respectable rhythm or back ground part.
If you have questions on how I did something in any of my songs....PM me.
BTW: while those instruments are considered to be classic country instruments, they are not as popular in Nashville these days. I actually had a Nashville industry source tell me to "lose the fiddle and steel" and send the song back after it was edited. Go figure..... they wanted crunchy guitars, not fiddles and steel guitars. If you are writing for Nashville, keep that in mind.