What is the most efficient way to make money in Gran Turismo 5?

Some of the Seasonal Events added in the recent update (1.05) have very good prizes. So far I’ve only attempted the 493hp GT-R race but coming 3rd gave me 340,000.

This update has also increased the rewards for winning races, but this is only in effect until the end of January 2011.

See http://blog.eu.playstation.com/2010/12/20/gran-turismo-5-functionality-update/ for more details.

Update:

After the release of the spec 2.0 patch, there is now a “Consecutive Login Bonus” – a bonus to both prize money and experience points. This bonus increases for every consecutive day you log into the game, up to a maximum of 5 days of increases.

The bonus is as follows:

• 1 day: 110%
• 2 days: 130%
• 3 days: 150%
• 4 days: 170%
• 5 days: 200% (ie. double rewards!)

So, make money even more efficiently by logging in each day for 5 consecutive days, then tackle some races.