Also, I'd love to see your math on the motorcycle saving you money on gas. As a motorcycle owner who closely tracks spending and mileage it has never been a net gain for me to own the motorcycle. I have a decently fuel efficient bike and low insurance costs and I still can't manage a net positive effect. Obviously I'm not against owning motorcycles, I just don't like the oft repeated gas savings that vaporizes after all costs are factored in.
I made a spreadsheet that compared cost per mile and savings of vehicle A vs vehicle B while still owning vehicle A. Made when I was shopping for another vehicle to figure how long an additional vehicle purchase would take to pay for itself. So essentially negative purchase price + savings per mile -insurance cost per mile for expected annual miles driven * miles. Plugging in numbers for truck at 13 MPG and bike as below, looks like the bike has paid for itself after replacing about 6220 miles in the truck. I did not include maintenance for the sake of this as I'm assuming maintenance cost per mile to be comparable per mile for any vehicle I drive. I do track that but have not put it into my quick and dirty spreadsheet as that was not within the scope of what I was trying to achieve.
These are my figures for an old Honda, a common and reliable bike
Bike: $1200
Insurance: $71/yr
MPG: 48
For someone who would own a bike regardless any miles the bike was used to replace miles in the truck would be saving $.19/mi using these numbers as it's $.07/mi for bike and $.26/mi for truck, assuming they use the same fuel. Any time I take the bike for a practical drive vs recreational is saving money... And also adding fun for a fairly low cost.
For the bike as a second vehicle with a goal of quick ROI and saving money long term, the bike absolutely does that too. At 6220 miles to ROI and after that $192 extra in your pocket every 1000 miles the bike is used instead of the truck.
If you're the type to not ride to work or other necessary driving and just lay down a couple hundred miles most weekends or ride after work... Well the bike isn't going to appreciably save money or significantly offset the fuel costs of a higher cost per mile vehicle the handful of times a year it may be used for necessary vs recreational travel. At that points it's just hobby or recreational spending and should be budgeted for as such.
If we're talking about any sort of brand new bike $15k-$30k or more and getting 30-50 MPG depending on what it is... That's as absurd as financing a brand new Prius to save on gas from not driving your brand new financed truck every day... IOW a mental justification for an extravagant luxury or status symbol that will never reach ROI and the actions show that spending less money is not an actual goal. A simple older bike at a grand up to a few grand can easily pay for itself as a second vehicle in a fairly short period of time if the intent is to save money vs driving a lower MPG vehicle and the use reflects that day in day out throughout the year.
MPG gains are diminishing returns. For a truck that gets 10 MPG, improving to 11 MPG is a significant savings. A car that gets 20 MPG, improving to 21 MPG is not too shabby. A car that gets 30+ MPG, it's pointless to even worry about MPG at that point as an additional 1 MPG is a drop in the bucket and not appreciable reducing fuel costs unless you drive a ridiculous number of miles a year. In my experience with various vehicles and running numbers over the years at various fuel costs, 20 MPG or less you can usually pay for improvements in fuel economy or reach ROI on a second vehicle in some reasonable timeframe.
20-30 MPG is a gray area where savings may or may not be significant depending on several factors. If fuel cost doubles then those ranges will shift, but fuel is historically stable in price so I see no reason to worry. For example take a 30 MPG car and figure adding an overdrive transmission at a total cost of $3000 will improve to 36 MPG, saving about $.02/mi in fuel cost. After 131,000 miles you're now saving money on that upgrade. Depending on use and total miles on the engine you may be looking at other major expenses then too, including engine/transmission freshening up. For most people you're also over a decade in the future. 30 MPG car plug the same numbers from the bike as a second vehicle example above and it's 27,000 miles to ROI which may be 5+ years in the future. My cutoff for doing something to save money with vehicles is 3 years but I prefer ROI within a year. Anything farther out is too unpredictable for me to justify the action as a money saving endeavor.
In any event, for me the numbers work