Yes it makes it very easy to shift features around to get a decent spread of easy and hard in a week / iteration.

It's also useful to have a check - more than a three day estimate basically means its too big - redo the press release

As for the floor cost - maybe. You still need to keep your feet on the ground at some point so increasing your rates and multiplying up is a fine approach. When you have an obvious winner go for much bigger rewards - but not everytime