It's not our money and we have no idea what's really "available" in United's treasury. 120m BP seems over the top to me but in 5 seasons such a sum might be viewed a shrewd investment.
The better question is whether 120m on Bale is a better investment than 120m on 3 other great players.
It might just be.
In today's world you're not guaranteed a great footballer any longer with a mere 40m transfer fee. You're guaranteed to get solid players (Herrera) at 30m, very good players (Mata) at 40m, but the truly elite players are now being purchased at 60m+. Bale went for 85m and is still probably worth at least that much, "worth" being viewed in commercial as well as pure footballing terms.
My view of our problem on the pitch is that we need a true box to box midfielder above all else. Fellaini is not the man for the job, nor is Herrera. Carrick holds the fort extremely well, but he doesn't have the engine we're looking for. Whoever the answer is, we need to address that hole in the squad in January or next summer.
If 120m on Bale precludes a deal for a top B2B midfielder, then I'm opposed to it. But if we can bring in the mid we want (say, Strootman or whoever we fancy) AND bring in Bale for 120m (hopefully less, at least on principle) then we're suddenly extremely scary even if we do nothing else.
Checklist:
Our keeper situation is in great shape.
I'm actually not too bothered about our back line at all, though I would like to see Varela brought in to cover (or challenge) Rafael.
We need a 6 midfielder to shore up what is otherwise a decent central midfield crew.
We could use a wide midfielder/forward like Bale, who has proven his mastery in the English prem and in the CL.
Our forward situation is more than adequate, although it's still an open question as to whether we should sign Falcao long term or not. That's another transfer fee question waiting to be answered. But I would love to see Henriquez given a chance with the first team. For me, the jury is out on Wilson.
Do this and we're scary. Very scary.
De Gea
Rafael Jones Rojo Shaw
Di Maria Carrick Strootman
Falcao Rooney Bale
...with van Persie, Blind, Smalling, Blackett, McNair, Januzaj, Herrera, Fellaini, Henriquez, Valencia, Young, Wilson and Varela (we probably have to let Evans and Mata go), and Lindegaard of course, as squad men is actually pretty ridiculous.
Adding Bale and Strootman (or Vidal, though I'm done thinking about him) to the existing squad, saying goodbye forever to Anderson, Cleverley, Nani, Chicharito and surely Evans as well -- selling Mata, sadly, unless he's happy to be a squad man for us but I think we'd want to cash in on him -- would be incredible. We'd be well poised to reclaim the prem trophy and compete extremely well for the CL trophy. And our bench players would be more than strong enough to compete well for the FA Cup and league cup.