I have thought about it this way too
I am going to need to get HVAC installed in our outdoor shed, and when I first purchased my place I figured the shed was nice to workout in, so there was plywood on one wall. Who cares if there is no insulation? So the windows were old, no important deal. Well in the wintertime it was just excruciating with how cold it was! I eventually ripped down the walls and ceiling to add insulation. I updated the windows with brand new. I figured if the shed was airtight I could get away with no heating and A/C, nope, I was still cold. I then tried to get by with a small area heater. In order to workout in the wintertide I needed to wear long pants, a jacket and gloves with the area heating system on. If I thought to preheat an hour before our workout, I could eventually take off gloves and a jacket. It wasn’t exactly warm in there though. Once summer time hit I knew that window AC wouldn’t do the trick. I was tired of never being the right temperature. I finally just bit the bullet and called our local heating and A/C business. I told them to install a ductless mini split and charge what they wanted. The initial cost was pretty darn high. The equipment is super extravagant, however the HVAC install rate wasn’t. I have thought about it this way too. If I had to spend money to workout in a temperature controlled area everyday, how much would I pay? I thought I would be willing to spend around 10-15 a day, which would spend money for the equipment in a little over a year. So that helps when I think about it that way.