I've been buying them piece by piece as I need them, rather than buying a set. Cheaper for the individual job, but probably more expensive in the long run.
The last one I bought (10mm) cost $2.99 at Trak Auto but I think that was on sale. The brand name was "Mr. Goodwrench" and it looked very good in quality.
Should be able to find these in Sears at a higher price. Maybe some of the other auto stores if you don't have a Trak.
Owner of the following Hex sockets:
5mm (Transmission Drain)
14mm (Differential Drain and Fill)
10mm (Starter bolts)