I'm going to say something that's potentially controversial, but it's been on my mind for awhile and I need to say it.
I think pro mastering is generally unnecessary and a waste of money for most home recording artists. The usual argument is generally that a pro mastering engineer will do a way better job than you will. I have doubts that that is even true, but let's just say that it is true for a moment. So what? I'm sure people like Sneap and Bogren will do a way better job mixing my tracks, but we mix our own tracks anyways since we can learn and control the way our music sounds. We can agree that many homemade mixes posted on this site are better sounding than some mixes made by pros out there. If it is acceptable for home artists to mix and track themselves, why should they avoid attempting to master themselves? Because they'll screw it up? But isn't screwing up a vital step in learning how to do anything?
I understand that mixing and mastering are different processes and that knowing how to mix doesn't mean you can master well. But knowing how to mix doesn't mean you can't learn to master well (I would argue that you're way better off than someone who knows nothing about mixing). It's not like the difference between mixing and mastering is like fishing and architecture. I think the general apprehension towards recommending a mixer to master something themselves roots from the feared notion that it would somehow be unfairly merging the two disciplines.
If you don't know how to make a redbook standard CD or how to edit PQ info, then learn it (that is if you even need it for you purposes). The money you'll save from mastering yourself can be used to buy WaveLab which allows you to do just that (and is used for applications in the mixing stage as well).
Now if you're a musician who doesn't record music, doesn't know what a compressor does, and doesn't want to learn, then of course you let someone else do it for you. However, if you are an enthused tracker and mixer, I think learning to master is a logical next step. A lot of music I enjoy listening to was self-mastered by the artist (Dimitar's latest cd being an example).