Well if I personally was making that much money in Toronto, as a super doctor for example, (Bosh's 16 million as a reference) - 29% goes to federal tax, 11% goes to Ontario provincial tax, so 40% total going to tax. So 6.5 million or so of that goes directly to income tax. 9.5 million left.
Then there's the player's association that takes 9% of salary figures to hold in escrow to make sure owners are covered that's about 1.5 million - so 8 million left. Agent fees are usually between 5-10% so that maybe another 1.5 million - dollars (though I'm not sure if that is recurring, or how that works, I think it's 5-10% of total contract value, meaning about 1 million a year). so 6.5 million left plus the 1.5 million in escrow.
I don't know if there's any other deductions that they'd be subject to, such as when they try to take the money from one bank to another, or deposit fees and stuff like that, or player's association pension contributions, Canadian pension plan contributions, unemployment insurance contributions etc., - and given that most of them have property/possessions that need to be insured/taxed at a much higher rate than the normal person, I wouldn't be surprised if bosh took only a quarter of that home in cash with the 1.5 million in escrow coming to him as well - so 8 million out of 16 after all the income/property/landtransfer etc. taxes, insurance and stuff go through, so ballpark is roughly 1/2 of their total salary figure. I'm no CA though, so this is just from personal experience.
This may be why certain NBA players go broke so fast - they sign a 5 year, 50 milion dollar contract and immediately buy a 5 million dollar house in case, and 1 million dollars worth of cars - then they realize they really only earned 15, 20 million in cash, and have essentially spent a year or two's salary already. (the equivalent of the average joe spending $100,000/year when they're working a $20/hr job)