The bearings themselves can be had even cheaper, their is and indentity number on the bearing if you can get that look in the phone book I found somewhere local that speciallises in all types of bearings. Only cost a fiver each!
If you are thinking about changing them Edde mentioned getting second hand hubs, most i've come across have had water ingress so I bought a set of 2nd hand hubs for £30 paid paid £10 for the two bearings and £10 to have them pressed into the hubs. Then when I had time just fitted the whole hubs assembly saved about £40!