hmm.. if you reduce latency from one second to a hundred milliseconds, could you celebrate that you've made it 10x faster, or would you have the same quibble there too?

Edit: Thinking about this some more: You could say you are saving 9x [of the new cost], and it would be a correct statement. I believe the error is assuming the reference frame is the previous cost vs the new cost, but since it is not specified, it could be either.