Yes it's more expensive
">You can do the same with battery backed storage (no need to copy initial data into it since it will keep its contents as long as the backup power stays valid).<"
You could do it by buying a unit that has battery back up to use as a drive which would save the time of loading it each time you start up, but, if you Have the 100 gigs of ram to spare to load it all on a ram drive and just load every time you start up, your start up time would take what ever time it took your computer to load it all to memory before it's usable. I'm sure you've noticed how in older machines even when you go from the logon screen to desktop, there's always something still loading when your just ready to roll with what ever it is you wanted to do. Well that times what ever your loading is going to be your load time.
And I see @mmstick1 has pointed to Linux which has for years sent out CD's and DVD's that could reside in modern memory and run happily. And dosn't take any longer to load.