Help with a savings calculator

Hello

I am after some help in creating the cost calculator, i have tried the using calculations route but i am struggling to work out how to get 2 comparing totals along with some more complex calculations.

https://www.laservisionscotland.co.uk/laser-eye-surgery-cost-savings-calculator/

Would someone be able to help/advise or is it not possible in gravity forms without extensive custom coding?

Thanks