Old, probably a re-post, but worthy.

So the husband was eating his breakfast and looking at the Financial Times and moaning about his investents being rubbish and not making much profits.

His wife smiled sweetly at him and said in an alluring voice;
'Surely, darling, I'M the best investment you ever made'.

He smiled back at his wife, thinking how pretty she still looked after 30 years of marriage, and replied;

'Yes, sweetie, you are. You are certainly the only investment that I have ever made that has doubled in size'.