From an ICC viewpoint, the penalty is in line with other instances of ball tampering

1994 - Atherton was fined $3700
2000 - Younis was suspended for 1 match
2004 - Dravid was fined 50% of his match fee
2010 - Afridi was suspended for 2 T20 matches
2013 - du Plessis was fined 50% of his match fee
2016 - du Plessis was fined 100% of his match fee.

Smith and Co's real penalty will come at the hands of Cricket Australia and Australian cricket fans who are far less forgiving.