I'd rather drop 30M euros on a player who may and right now looks like he will become a top player, instead of spending 15-20M on a player who we know will absolutely not turn in to a top player, or a bunch of more bench options.
We can't drop 60M on a proven WC attacker, this is a fact. So we either buy young stars in the making, or we play it 'safe' and buy more Pereyras. We can't compete with the mega rich clubs financially, but if we don't even take risks we'll never compete with them on the pitch either.