well i got a quote of 612euro ( inc vat) glad i was sitting down when he told me that. I tried another garage and he wouldn't touch it as its too labor intensive and I quote "an absolute pig to work on ) ah well it sits idle outside now until i raise the funds to get it rolling again .
If that includes parts (clutch kit) then it doesn't seem too bad actually.
I would try bringing it to an Alfa specialist to see if you can get a better price. You would probably get better service also.
There's a list of specialists in the stickies, or as David suggests if you provide your location someone might be able to suggest a suitable option.
My 147 1.6 cost about £250 for clutch kit, £30-odd for slave cylinder, and someone charged me £200 to fit it - which ai think he regretted, my mate's garage wanted £700 according to autodata it's an engine and gearbox out job.
If a diesel, you probably don't need to worry about the slave cylinder, but additional costs for a dual mass flywheel will likely apply.