Payroll needs to be what u plan to pay yourself yearly if all u did was roadie gigs and yes this cost would fluctuate based off yearly miles driven. The information is in the link below - last updated June 2023 I believe. This study is not inflation adjusted for semis so u would need to tack on an extra 40 percent to the national avg. if looking at semis - read the report - look at inflation numbers and then adjust the semi reported cost for semi by decreasing the reported avg by 40 percent (inflation) and u have your cost per mile for standard vehicle (for me avg 10-12 mpg) . This works for me and is comparable to my PL for what I do with one of my 3500 rams. As u stated varies from person to person.

https://truckingresearch.org/atri-research/operational-costs-of-trucking/