Well, if it doesn't cost much more than 100 times the price of a 128GB harddisk, it will be worth the price.
I don't care how fast it is - anybody who would pay £2,500 for a 128GB hard drive either has more money than they know what to do with, or is simply not wired up properly.Pertaining to database servers, I don't consider a faster hard drive to be the sole, or even a major contributing factor to the overall speed. So that's no justification at all. I also don't consider that a faster hard drive will somehow be 'easier to replace'.