These "legacy costs" are about $3-4k per car at GM, if I remember correctly.
Yes and no. As I've posted on other threads, my father worked for GM as a union employee for 20+ years so I a bit of insight into the past and present problems.
GM, like all companies (and gov't agencies) that offer their employees a pension, pays money into a pension fund each week/month/quarter. So the cost to a 100 year old company versus a new company (assuming both offered pensions) is the same - some percentage of payroll. There is no difference in operating cost. The only only difference between the 100 year old company and the new company is that the 100 year old company has (or should have) a huge pension fund. Many 100 year old companies have the so-called "overfunded pension" because not every employee stays on the job long enough to vest in their pension, so that saved-up money turns into a windfall for the company.
In the 70's and 80's when GM got in trouble, it spent its pension fund to cover operating losses. In the 90's, GM sold many/most of its non-automotive assets to replenish its pension fund - it sold EDS, Hughes Aircraft, DirecTV and Fridgidaire to the collective tune of $40billion. In the 2000's, GM again dipped into the pension fund to cover operating losses and now the retirement costs come out of operating expense, not the pension fund.
So, had GM not f'ed up and spent the pension fund, they would not have these so-called "legacy costs." 25 years ago, GM had a fully funded pension and $50b+ of non-core assets like EDS and Hughes Aircraft. Today, they have about $100b in debt (including the underfunded pension liabilities), no non-automotive assets and basically no cash. The banking crisis is a convenient way for GM to hide a problem that has been brewing for 25 years.
The gov't bailout of AIG makes sense; AIG has nearly $1tillion in assets and is profitable (on an operating basis). The losses are due to writing down bad assets but their core businesses make lots and lots of cash. A year ago, AIG was worth $200billion on the stock market - the US govt now owns 80% of AIG. The likelihood that the gov't gets back all of its money from AIG (times 2 or 3) is very good. $25B into GM will be gone in 12 months and there is no asset value to back it up.