There's a million different ways to look at what's worth it and what works for you. Yes, the bike may take thousands of miles to break even, but what if you replaced a car with the bike. Insurance and registration for my car could easily pay for an entry level bike every year, which is why we just have one car. That's not even considering the health benefits of the bike. That old truck you use to haul whatever once a year may cost you more in registration fees and insurance than renting a truck from Home Depot, but maybe it's worth it to you to keep because it has sentimental value. Being worth it doesn't always mean it's the cheapest or best option, just that it's the one you like.
Here's a spreadsheet I made years ago to compare the cost of doing a mod or upgrading to a higher MPG car. The numbers make more sense if you put the lower MPG/modification cost car on top (usually the current car), but I think it works out the same either way (it'll just be negative). The green cells are the ones you change to fit your scenario.
https://docs.google.com/spreadsheets...it?usp=sharing (I think you have to save it to your Drive or computer before editing)
Here's the formulas for those who can't download it or want to make their own.
