Actually there are...
Some engineers donch feel comfortable in mastering albums becuz this is not their area of expertise. Some studios offer such services like The Void @ MFG, Lion Studios (the live room looks insane from the photos!), Focal Pro Solutions, etc. There used to be a joint called The Audioplex in Tampines where quite a few Singapore big acts had recorded their albums.
Mastering is usually a combination of equipment and experience.
Check out Masterdisk where the Great Spy Experiment mastered their album at. The bloody console looks like it can be used to launch a few lunar missions. Then again, the experience of the mastering engineer plays a big part. When you eat, live and shit mastering, I think you should be, ideally, quite good.
Locally, mastering usually will set you back around $100 per hour. Some places charge $100 per track. There are stem-mastering and pre-mastering mixing as well.
Good luck. Have fun.