Benatia wouldn't be cheaper than €30, AS Roma are determined to keep him and Barcelona and City really want him aswell. If we could get Benatia for that price he would certainly be preferred but the reality is he probably completley out of our league, he might not even leave Roma at all and if he does, he'll have Barcelona or City written all over him.
Marquinhos would cost an arm and a leg, PSG paid more for him than €30m and they wouldn't sell him without a profit, and again this guy is heavily linked with Barcelona to the point that alot of media suggest a deal has already been made for Alves and €20m (not saying those media are true, but it is an indication, that we aren't just going to come in and snap him up, definitley not for €30m). On top of that marquinhos is 20 years old, doesn't speak a word of english, he may be a great talent, but we have talented centrebacks with the loss of Vidic and Rio we should rather be aiming for experience.
Considering Garay I'd say he is not the type of centreback LVG needs to play his kind of football, he needs a playmaking centreback and I don't think Garay would suit that role. On top of that is widely reported his move to Zenit is already a done deal. I don't think Garay is even available anymore.
We can also all talk about somebody like Hummels but I simply don't think we make kind of chance to sign these players. Mangala possibly, but Chelsea are after him and even City found that his price tag was to expensive, so I doubt we could afford him (wouldn't make more sense than Mirranda).
I'am not saying we should sign Mirranda for £24m because I agree it is a bit much for a 29 year old, yet saying many other (better) players are available for less is simply not true. If the move would happen, I would be a little fed up about the price tag but beside that I'd think we have ourselves a great centreback for the coming 3 years under Van Gaal. A highly experienced player, the type of centreback we don't have here at the club, playmaking, easilly scoring aswell. He would help LVG to build the kind of system that matches his football vision and he could help Jones and Smalling in their development with his experience because its clear neither of them are really ready to lead back lign just yet. On the short term it would be a good signing, but it would be an expensive one because there is no long term value in it.
But rather Mirranda for £24m than nobody or rather him than BMI thats for sure.