Read up on Balanta and watched some clips after Tata was first hired and rumours of wanting the defender started to crop up. Still seems a risk, IMO. Strong, good left foot and has good composure for a defender. Truth is he reminds me a little of a stronger, more stout, Mascherano - had he started out as a defender instead of midfield. Seems to understand the 4-3-3 system well, plays that left sided CB role and has decent acceleration to close down although lacks actual pace. 1.81m so not really solving our height issue in the backline although he supposedly is good at heading the ball.
A technical player which would suit Barcelona obviously and has the strength & aggression you'd like from a central defender without being dirty. Probably would be in the neighborhood of €10-13 million but wouldn't come without a risk due to his relative lack of experience. Still, if you're going to gamble, better gamble with cheaper players than 30 million