I'll throw in my two cents worth -- even though, as several posters have noted, it is possible to learn to do good machine quilting on a home machine, it may not be your wife's cup of tea. Some people enjoy the piecing or applique parts of quilting, but have little interest in quilting (assembling) their own quilts. Others enjoy quilting for others more than piecing their own. Still others enjoy and are proficient at all the steps.
I think it's reasonable to do what you like and can do to satisfy your own level of perfection while leaving the other tasks to someone else. No reason to turn an enjoyable activity into drudgery by forcing yourself to complete every step yourself, especially if you enjoy only one part, like piecing.
That said, your wife may enjoy learning to machine quilt and finish her own quilts, but if she does not, less than $200 for quilting a queen-size quilt is reasonable. She may want to learn to attach her own bindings -- a relatively easy task to do well -- to save the extra $30.