Depends what we're looking for as a club. If it's 'just' to improve the team so we would stand a better chance of winning the CL, then players like Gundogan are perfect and we just need to improve the first team where necessary. If we're looking to sell shirts, or at least get the fee back via shirt sales, then there's a handful of players that could be. And I'm not sure it's Pogba today, although a decent Euros and he could reach that bracket.
Kaka aside, we've never tried to sign a galactico, for which I'm glad, but the entire Barca business plan was built around that to elevate their commercial side. If we're going £60m+, IMO, it'll be for a shirt seller as much as what they bring to the team, although the two go hand in hand. PSG and Chelsea have spent a lot on players, yet how many kids do you see in their shirts compared to Barca or Real. I suspect something big is coming to move us to the next level off the pitch to go with the success that Pep will bring on it.