Icardi CL experience is 6 games in group stage last season. His NT experience is 8 games in friendlies and WC qualifiers. The teams he has played for in Serie A have finished 4th twice, both times barely, all the other seasons it was lower. I think it's safe to say that at 26 he has never been tested on the big occasion, it's one thing to score against Juve when you're trailing 26 points behind and quite another when you're locked in a title race.
I think both Icardi and Lukaku on the current market cost ~70m as both are relatively young strikers that guarantee you goals. Paying 160m for Icardi is a stretch, this summer he's available on a bargain yet they can't find a buyer.
We shouldn't buy neither though as we already have Ronaldo, Dybala, Mario and Kean, all of whom are one way players, you can't have more than 2 attackers in your lineup in modern game.