Labour and antiques are well priced here, so you can get great stuff built, restored, and you can snap up bargain antiques. There's some great pieces in mercado de pulgas and the surrounding area.
I've picked up amazing 60s design pieces, beautifully restored for the same price as a self assembly piece of junk that Easy are selling. Really depends what you need, but I'd go with a combination of restored antiques and skilled labour to build what you want. You'll get the best value and the best quality that way. Might be more than Ikea, but its money well spent.