Certainly, under those circumstances, I'd be tempted to consider paying $50,000 to have our 18-year-old cat Shadow cloned, although I gather the cat cloning business isn't going so well. People raise ethical questions about cat cloning, rightly enough given all the unwanted strays, but Shadow, with his astonishingly good temperament (if we could recreate it), surely is a special case.
Today I found another use for that mythical money, upon reading that a mere $10 million could bring to life a reconstituted woolly mammoth. That would be an easy call for me if I had a billion. And sign me up as well for the reconstituted Neanderthal that (whom?) the article discusses - ethical questions be damned when you think of how astonishing this would be.
Before getting too excited, I should note that, while I haven't yet checked today's stock prices, as of yesterday they didn't appear to be heading me in the direction of a billion dollars. Indeed, these days zero is starting to look a lot more likely.