I think 40+ million for Gueye is not going to happen. PSG wanted him in January when prices were high and yet they didn't even meet our price. In the summer they can take their time and find someone else if Gueye isn't available for a reasonable price.
For a quasi-sovereign entity like PSG, success is the only currency. How much they pay for players really doesn't mean much to them, and if it means spending an extra £10m for Gueye, it's irrelevant. Even with Financial Fairplay rules around, they still don't seem to care.
For a top player like Gueye, where he is on a long contract with 3 years left, and is the type of player in rare supply, we have a valuable commodity on our hands. If they want him, make them pay over the odds.