Tim Carney has a terrific column on the legislative history that led up to the prescription drug kerfuffle I read about last week. It makes something clear that I found hard to explain during the back and forth with commenters (as I said to Tim last week, this is the most semantically complicated, and yet least actually complicated, issue I've tried to explain in a long while).
Say you have a company that in 2002 was providing drug benefits to its retirees at a hypothetical cost of $2500* per retiree. Each $2500 you pay reduces the taxes you owe by about a third of that amount, so the actual cost of the subsidy to the corporation is about $1700.
In 2003, the Congress passes a Medicare prescription drug benefit. Worried that corporations would drop their benefits and stick the government with the tab, they offer a subsidy for firms that continue their retiree drug benefits. That subsidy, 28% of the total benefit cost (up to a cap), costs the taxpayer on average much less than providing the drug benefits, so it's a good deal for the taxpayer.
So now the cost to the company for these benefits is $1700-700 or about $1000. The cost to the taxpayer is $2500-1000, or about $1500--still slightly less than Medicare pays for the average Part D beneficiary, but for much more generous benefits. One can argue about the economic distortion, but it's not your traditional "corporate giveaway". If it's a giveaway to anyone, it's to corporate retirees.