I need 4songs mastered.

I'm a "smooth jazz" guitarist, along the lines of George Benson, Norman Brown. I'm in the process of finishing 4songs and trying to get a line on Mastering Studio procedures and pricing. One cut has vocals(4:30) and the other three consist of music only (3:52 / 4:08 / 4:00 . The main instrument is guitar with some horn section backing. About what would it cost to master these songs ?

Additional info:
I'm interested in working with a very experienced mastering engineer. The song is mixed and ready to be mastered. I don't have a hard deadline for this.