If it was 70 million including add ons, it looks an okay fee. Especially if some of them rely on him actually succeeding, which is obviously a much better add on for a buying club as it prices in them not flopping. Benfica probably wouldn't like that though, and their whole ethos is attracting very large fees for players that are still to be proven in a top league. So it's always a little risky. But the market is really difficult for strikers, that is going to be a thing we have to accept, and the level of interest in this guy will probably dictate where he lands within that range.
It's probably going to be a bit cheaper than Harry Kane. I really don't see Harry Kane being sold to us for 70 million. It's very hard to imagine them going for that. It would be pragmatic to do that if we were the only interested party because they could strengthen their squad and not lose him for free, but I just don't see them packing Harry's bags to Man Utd for anything else than close to 100 million.