I've done a fair few now, and the total usually comes to around £300 - that's everything included - Audi matrix, pipes, clamps, a recon heater box with the flaps freed up and lubed, new foam on the top of the heater box, retaping the ducts, all the labour - and on the last one a replacement blend motor, as one was faulty and it's not worth going back in a second time to re-do it.
You don't have to take any of the wood trim out to get the top of the dash off. (it is actually proper walnut... yes, a thin veneer on a metal backing, but all of the actual LR pieces of wood, were genuine wood - not some fake stuff.) Usually when you try and pry the wood cappings off, either it bends the metal backing/cracks the wood/lacquer or pulls the metal pins out, but you can get the dash off without touching them.
The passenger side one is listed as having to come off to get the passenger air bag out - but with a couple of trim tools, and the bolts from the airbag removed, you can actually get the airbag out with a bit of persuasion, and without damaging anything. On refit, the trim tools just help get the lugs on the front of the airbag unit back past the trim and it will slot back in and bolt up.
The only thing on ones I do that gets cut is the supports to the face air ducts behind the airbag on passenger side, and behind instrument cluster on the drivers side - these are held in with one screw and were obviously installed before the dash was mounted in the factory - cutting these supports gets the duct out and gives access to the bolts that secure the top of the dash to the frame. On reassembly, the sliding joint, and duct tape (also hand to seal up the joins, it's amazing how much more air you get out afterwards!) are sufficient to hold the duct in place.
If you decide to go that route as a DIY, then I can supply audi heater core kits - and also can help with advice/pictures etc of the process when I've done it before.