I had thermostats in every room with electric baseboard. I have good airflow in summer and A/C was not a concern. But with my GF moving in and having allergies, I had to lock up the house.
The geo is well balanced and comfortable. Bu that is more of me working with the ductwork designer on every duct and outlet.
Geo does have a long payback but it does last more than 20 years. And geo works well no matter how cold or hot it gets as opposed to air units. Typical local costs for heat cool for my size house are $3500 or more. I think I am at $1200 for the year. With $15k in cash back, I expect it will take 10 years in a house that is more comfortable than an air unit. And like with the mortgage being paid off, things get a lot cheaper after that.
For a lot of people, it is not worth the investment, it is like a lot of things. Most people who have campers probably would save money by just staying in motels.