Best Practice: Don't Spill Your Candy In The Lobby

NEVER tell a prospect how much money you can save them before getting as many committments as possible!  This also goes back to not "spilling your candy in the lobby".
It's important to build your case and earn the trust and "buy-in" long before going for any sort of close!
Example:  "I did the math, and we can save you $1000 per month..." - You gotta show your work!  Build trust by taking your time and convincing the prospect to take a moment or two with you to go over the differences in a few popular chargetypes!
Work on lulling the prospect into a "frenzy" of animosity toward their current payment processing provider and then prove why your customized solution is the right solution!