I think from the standpoint of propane use you have to think very long term to recoup the price difference. You are talking ~ 0.2 pounds of propane saved per 6.5 gallon boil (Blichmann's data). So if you are doing a 6.5 gallon boil you need to brew 100 times to save yourself a tank of propane.
I think you have to take everything into consideration to justify the cost.
-Stainless steel so you will probably never replace it.
-Has a low gap between burner and kettle so works better in wind and has better heat transfer to kettle.
-More efficient than most burners (Becomes more important as you go up in batch size).
-Plugs right into top tier system (if that's important).
As far as large batches go (1-2 barrel systems), Blichmann engineering has suggested that people use a commercial stock pot stove. Something like this from American range
. The one linked sells for around $450 new.