Miche makes them for Shimano and Campagnolo, and I'm looking at the 30-tooth alu cog right now. This cog is very slick and very light. All things being equal, a 30 tooth cog should wear at 1/3 the rate of a 10.

If you replace your chains at no more than 0.75%, or 3-4 chains for every cassette, the alu cogs should last a long time.