I have never paid to pack wheel bearings, but it is very easy to do. I would think ~$20 labor for both sides would be a fair price at a small mechanics shop. You will probably need to buy a set of inner dust seals as they need to be removed for the repacking. They are pretty inexpensive.
What to watch for; When you drop it off tell them if you need any parts you want the old ones, that way they will not be able to charge you for something they didn't do.
If you don't have an independant mechanic you trust, ask your friends or neighbors who they use. Most people know someone they trust.
good luck.