Its easy to weigh the sets from Ebay
It looks like each year can vary just a couple of tenths but I weighed the 2005 Silver and Clad Quarter proof sets and here's what I found out.
All 5 Silver Proof Quarters with the plastic case = 76.8 grams
All 5 Clad Proof Quarters with the plastic case = 73.2 grams
It might help if someone has all the sets straight from the Mint to weigh them and post all the results so we can protect ourselves from cheats!