Earlier quoted context omitted.
> You can't easily replace the frame though. You can. You just move the motor, battery/controller to another bike. What the author did is a great way to check the feasibility of the idea for himself without breaking the bank.
It took him ten hours of work the first time. Yes, it'll take him less the second time because he's gotten better at it, but it's still by no means easy or trivial. And we haven't gotten to how much he values his time yet.
Don't weight ten hours of learning about bicycle assembly as though it were ten billable hours if it isn't. Compare it against the ten hours you were going to do other things in: reading, watching TV, going out for a walk, whatever.