Steven Spielberg: If Only I Would Have Kept that House ...

Steven Spielberg may have the same regrets everyone over 40 feels about selling that house back in the day ... because had he held on to his Malibu estate 6 months longer he might have scored an additional 9 million bucks!!!

Steven unloaded his 7,200 square foot beachfront estate back in August for $26 million. He made a handsome profit because he bought the 7 bedroom 10 bathroom home -- with a theater and a pool -- for around $6.6 million in 2 separate transactions ... he got on lot in '89 and another in 2000.

Well 6 months later hot-shot realtor Chris Cortazzo from Coldwell Banker in Malibu listed the same property for $35 million.

There is something to soften the blow. Steven's reportedly worth $3.6 billion.