Hmmm... I never find a good deal on aluminium on Ebay. However, Trident here in Austin has also been great! Another company here in Austin wanted $158 for a 4'x12'x1/8" sheet of aluminium, and a 4'x6' half sheet was $147 due to the "cutting charge and higher price per square foot". Trident sold me the same 4'x6'x1/8" 5052 alum for $58.
I like Home Depot stuff, but I worry them on my car, especially those grade 5 bolts that I can pop with a hand ratchet.
Cheers,
-Neil.