Bloody hell. Talk about building up Pogba into some sort of footballing "god". Suddenly Alli, who has shown at least as much Pogba ever did at the same age, is not fit to be mentioned in the same breath.
I fear you're going to be sadly underwhelmed if this transfer to the Prem occurs ... money-snobbery is severely clouding your judgment. A £100m fee does not make a player world class, any more than a £4m fee makes a player "bang average".
This is the FIFPro 2015 World XI and their current ages in brackets
Neuer (30)
Alves (33), Ramos (30), Thiago Silva (31), Marcelo (28)
Iniesta (32), Modric (30), Pogba (23)
Messi (29), Ronaldo (31), Neymar (24)
With the exception of Neymar, everyone else on that list is at least 5 years older than Pogba and in the attacking six Iniesta is 9 years older than Pogba. He's already been voted as one of the best 11 players in the world by 40,000 other professionals and is the youngest player on that list. Going by an average top player's trajectory, he's probably got another 7 or 8 years as an absolutely world class player and then still three more years of still being one of the best players in whichever league he's in, if not in Europe. For rich teams with Champions League winning ambitions, only the very best players will do and £100m for a projected 8 year period of being world class actually works out at quite an easy £12.5m per year. If you buy Modric at 30, £100m it makes way less sense because you've got way less time to get the value out of him to repay your outlay but for the world's best 23 year old, it's been the going rate since Ronaldo and Bale made their moves.
As for whether or not a club should pay that much money, if you look at the amortised cost, £12.5m + wages is easily affordable for a club who turnover almost half a billion pounds per year. Heck even £100m up front isn't even too much of a stretch for a club making that much money and then you've got Pogba with only wages to pay from then on. Do clubs have too much money to spend? Well there's millions and millions of us who shell out hundreds and hundreds of pounds each year to watch sport on TV and local fans who spend millions and millions on matchday tickets and food and VIP boxes over the course of a season. Its a professional sport, we pay them money to watch their sport, its not as if they rigged LIBOR or ran a ponzi scheme to make their money. If you want good honest local sport, go to your local park on a weekend but this is pro sport and its going to make money as long as its entertaining.