Yeah, I'm ignoring those items completely.
I agree with your reason for doing this, but when people say "I only spent $xxx", it isn't a real number that other van DIYers can really use for budgeting.I have decided not to count all the things I have bought and changed my mind about in the final budget tally! 😆
The "real cost reality" is that everyone has items that are left over or plans changed or turned out to be prototypes.
I think that it is also worth to assign a value to your time. For example $10 / hr.
There is nothing at all wrong with a hobby / DIY project, but if you always price a project based on the materials costs, it might not be the ideal way to do it.
When you are 70, what would you pay per hour to be 30 and off doing things vs drilling every hole or a part of the project that is not your strong suite vs being out on vacation?
The answer is different for everyone, but I believe that putting a value of $10 / hr on your time helps to drive the decision in a good direction.