I'll start with some basics - those who know the CBA can skip ahead.
Salary Cap
2011-12 - $58,044,000
2012-13 - $58,044,000
Exceptions
Mid Level Exception:
- $5m, with 3% raises up to 4 years, for teams under the luxury tax threshold last season; or
- $3m, with 3% raises up to 3 years, for teams over the luxury tax threshold last season; or
- $2.5m, 3% raise up to 2 years, for teams under the cap for use once they have used their capspace.
Bi-Annual Exception:
- $1.672m, up to two years, for teams who did not pay luxury tax last season.
Luxury Tax
Threshold typically $70m ($70,307,000 for upcoming and prior two seasons)
A key thing to note here is how punitive the luxury tax is compared to before. The old CBA provisioned that for every $1 over the tax threshold a team goes, the team pay $1 luxury tax into a tax pool, which is redistributed to non tax paying teams at the end of the season.
In the new CBA, tax changes go as high as $4.25 for every $1 beyond the threshold, for teams well in excess of tax limits for four seasons. In its simplest sense, if you have a payroll of $85m, and offer someone a contract for $1m per year, you will pay $1m to the player and $4.25m to the tax pool for the priveledge.
Quick reference guide: http://en.wikipedia.org/wiki/NBA_salary_cap
More detailed reference guide: http://www.cbafaq.com/salarycap.htm
Miami Heat Financials
http://www.forbes.com/teams/miami-heat
For the 2010/11 season, Forbes estimated $158m turnover and $26m operating income, based on a $69m payroll. A successful season, considering we did not pay the luxury tax and the big 3 brought new excitiment to Miami.
We can make an assumption here that other operational expenses, e.g. arena operating costs, general staffing costs etc, are $63m, a figure I'll refer to later.
($158m - $26m - $69m = $63m)
Miami Heat Tax Payments
Now, our player contracts project at something like $80m / $84m / $84m for the next three seasons.
Assuming the lux tax threshold remains at $70m, we will have the following tax bills:
(Year - Salary - Tax Bracket - Tax Payable)
2012/13 - $80m - $70m = $10m = 1x tax (old CBA) = $10m
2013/14 - $84m - $70m = $14m, $5m taxed at $1.50 = $7.5m, $5m taxed at $1.75 = $8.75m, $4m taxed at $2.50 = $10m. Total tax $26.25m
2014/2015 - $84m - $70m = $14m, $5m taxed at $1.50 = $7.5m, $5m taxed at $1.75 = $8.75m, $4m taxed at $2.50 = $10m. Total tax $26.25m
Those figures look insane under the new CBA. Total payroll per season inc. tax:
$80m + $10m = $90m
$84m + $26.25m = $110m
$84m + $26.25m = $110m
The team will also likely have seen a revenue jump due to winning the title. I'll be generous and suggest $10m. So:
2012/13 - Revenue $168m - $63m costs - $80m payroll - $10m tax = $15m operating income
2013/14 - Revenue $168m - $63m costs - $84m payroll - $26.25m tax = $5.25m loss
2014/15 - Revenue $168m - $63m costs - $84m payroll - $26.25m tax = $5.25m loss
(worst case would be identical revenue, followed by £5m profit, and £10m losses x 2)
Summary
Even with additional income, the franchise is going to make losses for two of the next three years, due to the extortionate tax bill Arison faces. Whilst he is a wealthy man, remember this loss is before interest payments on any loans (which we do have) therefore is clearly not sustainable, particularly as it could easily increase if we were to use our exceptions in following seasons.
Other Financial Stuff
There were talks of a new TV deal, but I understand these were false and nothing is signed. It would be purely speculative to take this into account in the above.
Amnesty Options
Amnestying Mike Miller is an interesting option. Assuming we are confident enough to replace all his minutes with Battier, Jones & Ray Allen, I've worked it through the financial model:
2012/13 - $74m - $70m = $4m = 1x tax (old CBA) = $4m ($6m difference in tax)
2013/14 - $78m - $70m = $8m = $5m taxed at $1.50 = $7.5m, $3m taxed at $1.75m = $5.25m; total tax = $12.75m tax
2014/15 - $78m - $70m = $8m = $5m taxed at $1.50 = $7.5m, $3m taxed at $1.75m = $5.25m; total tax = $12.75m tax
The tax difference in years 2 and 3 is $13.5m per year, which is pretty significant. I am not surprised Riley isn't amnestying him now, but I would be very surprised if he goes past next summer.
Don't forget if we amnesty him, we still pay him, it just doesn't count towards our salary cap...
Thanks caneaddict for helping with the numbers
Hopefully that TV deal comes to fruition. 
Everyone became a CFO!!! If you leave player personal decisions to these realCFO's (lol get realGM, realCFO) our pay roll lineup would look like this:
