Most the time that is true although often if you book at the last minute it is cheaper on the Spirit of Tasmania than flying. I recently booked a flight for someone from Melbourne to Hobart a day before departure for $329.00AUD (this is a common price for a late flight booking when it has low availability) and the Spirit of Tasmania can cost as low as $99.00 per person at this time of year (the shoulder season) or as low as $69 per person in the winter time (off-peak season) in an Ocean View Recliner without a vehicle. The Ocean View recliners are not the most comfortable things to sit in overnight, but still $69 isn't too bad at all when you consider the cost of a last minute flight. If you book well in advance then it is usually far cheaper flying than getting the boat. here