Agreed with Centerline. Ground is critical but many CFI's minimize it to speed up their own flight hours or because they're paid less/not at all for it.
I worked 40-70 hour weeks as an instructor, a bad month was $1200 before taxes, a good one was $1600. But that was less than all the surrounding flight schools. If you're around $2000 or better a month, I think that's decent for an instructor (though still not what the profession, skill set, and responsibility deserve).