Correct, people often say CGT is 50%, but as you say, add the...

Correct, people often say CGT is 50%, but as you say, add the capital gain to your personal tax and you pay tax at your marginal rate.

If your taxable income is $100k per annum, and make a $50K capital gain (after expenses) then your tax liability on the $50k would be whatever your marginal tax rate would be for that $50k. If you hold for more than 12 months you get a 50% discount on the CGT payable. If you are in the top marginal tax rate then you would be paying about 25% on your capital gain.

If you own through a trust the CGT payable is based on the marginal tax rate of the beneficiary person/entity.

If held through a SMSF you pay the standard 15%, which is discounted to 10% if held for 12 months or more.

This is all generally speaking, but really is something that depends on individual circumstances and it's important to get good advice based on individual circumstances.