Marotta did fail on that one. Actually it's one of his biggest failures.
He reached an agreement with Pescara. He'd pay stg like 2.5M + 1/2 Buoy for 1/2 Verratti, who would remain another year at Pescara.
Than Raiola said no, Buoy ain't going to bloody Pescara.
Pescara president then said: OK, gimme money to compensate the absence of Buoy. Around 1/1.5M.
Marotta played hard ball, refused, wanted a discount. The negotiation lingered and then, just then, PSG appeared with a whole shit of money.
Summing it up: Marotta misjudged potential. Had he increased the offer in 1.5M, paying 4M for 1/2 the player, Verratti would be joining Juve this summer.
I know he played in Serie B. But didn't he pay 4M for 1/2 Gabbiadini, who had barely played for Atalanta? 5M for 1/2 Boakye, who used to play for Sassuolo, also in Serie B? He refused to pay 4M for 1/2 Verratti, as simple as that. He considered Gabbiadini and Boakye to have more potential than Verratti. He even payed 2M for Bonatini, 1.7M for Masi, ffs, 4M for Leali, who is much less proven.
So yeah, Marotta fucked it up big time. I consider this one of his biggest failures. But he had a lot of beautiful deals too. Pirlo, Vidal and Pogba, the best.