You have to ask for money. Not only is it good for you, it's excellent validation for your product. If no one is willing to pay for your product then it means you need to go back to the drawing board. If they are willing to pay for it great.
Like say we make X 50% more efficient, we expect to get paid the full 50% efficiency since its now 50% more efficient forever. The Q is how do I bridge the gap to ask them to pay.
"All right, you've seen what we can do. Let's talk money."
"I hate this bit, but just so there's no misunderstandings down the line, let's talk money"
And don’t undervalue yourself, find out the equivalent prices in your area or what figure out what brings a profit and set that bar.
A 50% efficiency increase could add value to your customer, why not make it an premium product/subscription/version? So keep your old clients on the base version for instance, or offer them the premium.