With Musk the right question is never 'will it work?" but 'will it make any sense factoring in the costs?'
That is the great thing about having billionaires with the curiosity of engineers. Musk is willing to find out if these 'crazy' ideas make any sense factoring in the costs. Let your average VCs fund the companies whose ideas will most likely work. Men like Musk are the ones with the freedom to investigate the ideas which will probably not work, but would be phenomenal if the general wisdom is wrong.
IMHO Musk is filling in for governments who aren't spending enough on basic research and grand innovative ventures. For these projects it is expected that you will fail far more often than you succeed, which is why traditional investors stay away. I hope Musk keeps up his current pace of innovation for the next 30 years.