I'm in no way saying he is a Lukaku, but there are many players with abilities similar to Maddison. The only reason he would cost that much is that he is English and plays for an English club with enough money. Half of his key passes (assuming passes leading to a shot?) are from set pieces. Statistically, Maddison seems to be the better passer, and he is better physically compared to Felix. But Felix is still not physically in his prime, he is two-footed, his technique is silky smooth, he seems to make the right runs and decisions and got a great understanding of the game, he is not afraid to go into duels...
I can understand people arguing that buying Maddison would not be so riskful as going after Felix, but I think Maddison is not likely to become any better. Felix, on the other hand, got the fundamentals in place of becoming a world class player.