Sachs don't make a DMF
You use the stock LUK DMF which can be bought for £250 from buypartsby.co.uk
Sachs clutch from Sachs costs £550 so thats £800 plus £600 for fitting?? (£1400) You also have to buy the clutch release bearing from Audi but that's buttons in price in comparison.
It is a 5-6 hour job to fit all parts so you are getting charged £100 labour per hour??? seems a bit steep if you ask me!
A quick google search showed me this difference:
SMF = single mass flywheel
DMF = dual mass flywheel
The smf is a solid flywheel like most cars have, and they use a clutch disc with springs (damping) in it. The DMF is a dampened flywheel, two pieces that have springs between, and uses a clutch disc with no springs (damping). The downside to a dampened flywheel is that they wear out, and are expensive to replace, versus just surfacing a solid flywheel and replacing the clutch.