Is it worth buying for parts? I'm assuming that you would use a different frame, headset, and tires here.

6600 RD: $60
6600 FD: $50
6600 Cranks & BB: $140
6600 Cups: $25
6600 STI levers: $300
105 Cassette: $55
105 Chain: $20
105 Brakes: $60
105 550 Wheelset: $250
Selle Italia XO: $30
Ritchey Logic SP: $30
ITM Racing Stem: $23
ITM Racing Bar: $35

Total: $1078

Prices are from Google Shopping. So not really a good buy if you're just going to toss the frame in the dumpster. Plus, you are buying older parts - 6600 Shimano Ultegra instead of the newer 6700, and 550/5500 105 instead of 560/5600 Shimano 105.