it is very possible for your wife to learn to quilt with her domestic sewing machine- many very (big-name/famous) quilters quilt on their sewing machines- the easiest way to learn is to take a class at a local quilt shop-or watch videos /tutorials and practice- there are many tutorials- and books --it does take some practice-
many other quilters===beginners and pros send their quilts out -- she should learn to do her own bindings--that part is easy enough for any beginner- again she just needs to watch the tutorials- but a simple explanation of bindings is---you sew 2 1/2" strips of binding fabric together to reach all the way around the quilt + 10" or so===fold it in half (wrong sides together) and press- then line up the raw edges with the raw edges of the quilt top- stitch it to the quilt by machine (check tutorials for mitered corners) then you fold it to the back of the quilt and hand stitch it down (which is what the long-armer charged you $30 for)
the guys in my family (son's and nephew) are all quilters- and are very good at machine quilting on domestic machines- they started with small projects (about 18" square) put together top, batting, backing- marked how they wanted to quilt-and sat down and practiced- when they were happy with how it was going- how the stitches looked they made something larger- it didn't take long before they could handle king sized quilts ...best to start small-and practice---but totally do-able. my first quilt i sent out to a long armer---it was a shocking $385 for me to pick back up (and he did not do the binding for me!) at that point i figured i could never make another quilt- unless i learned to do that myself! i could never afford that! i was not expecting that price at all---i had been told the charge was 2 1/2 cents a square inch---didn't sound like that much...and the quilt was for my daughter's wedding present---so ...anyway---
it is not surprising how much it cost- but it does not have to be that expensive for you if you want to learn---i know guys who seem to be much better quilters than most of the women i know- maybe you could make it a (couples activity) she could piece- you could quilt!