Its not a tax write off, I really hate how often miss used and misunderstood that expression is.
Its an expense paid by the corporation. The expense is justifiable because it is used to entertain clients who give them business.
The expense is against taxable income, thus it reduces the amount of income taxes you pay, but its an expense not a write off. It means the company still pays about 80% of the tickets. And if its a publicly traded company, you do have to answer to the share holders for the expenses.