$6 would be about right for that grade of bearing, there are other threads about where to get them and what model to get that I'm assuming you've found.

I wouldn't bother with this unless your bearings are trashed and you haven't tried just regreasing them (yes, you can service formula bearings), it's "better" but we're really splitting hairs here. It's not worth throwing good ones in the trash, the point is more that if you're going to replace crunchy ones the cost of upgrading to the best is minimal.