The trick to finding deals at the pulgas is to go often, and to know what you are looking at.
My wife and I have found some incredible deals there- she recently bought a Saarinen side table there for about $150 US that goes for about ten times that on Ebay in the USA, and triple or quadruple that at furniture stores in Buenos Aires. A new reissue of the same table at Design within Reach is $1200 US. Ours is original, and worth more.
But she had to be quick- it wouldnt have been there the next day.
If you get to know the dealers there, you get better prices.
I wouldnt buy upholstered furniture there, though, unless I was willing to have it completely reupholstered. Upholstered furniture, in general, used, is kinda an iffy proposition- who knows what people, or animals, did on that upholstery before you bought it?
We did buy a cast iron claw foot bathtub at the Pulgas, but for about a quarter of the price mentioned above. Of course it didnt have griferia- but griferia is one of those things you want new, not 80 years old. 80 year old rubber washers leak every time.
You cant buy a new claw foot free standing bathtub in BsAs- if you go to the big plumbing supply places, they have $4000 peso bathtubs, and they are all meant to be built in to the wall and tiled. If you want a claw foot, the pulgas is the best place to look.
I would also agree that Scalabrini Ortiz would be a good place to look for custom upholstery- there are several places there south of Cordoba that build to order, and, if you want cloth rather than leather, it should be in your price range.