It doesn't need to have a financial gain, but it needs to have some clear benefit/gain. (see GC/GWS and the supposed 'grow the game' benefit).
Given a Tas team wont grow the game appreciably (it might slow/reverse decline in Tas a bit, but the numbers wouldn't be huge, especially as the problem is more about demographics and societal changes than having a club), then it either needs to show it wont be a multi million dollar financial black hole for the conceivable future, or that it has another real benefit (i.e. something other than sentimentality and empty gestures).
So, if not financial benefit, what benefit would a Tas team provide?
Few hundred thousand extra AFL fans. It's clear that Tas wants it's own team and would back it in.