You have to price your labor at the value of the service. The cost of the laptop is irrelevant, as is the fact that you haven’t charged in the past.
Your rate is reasonable for a one off business software migration to a new machine. I’d invoice for 2.5-3 hours since the labor most likely involved a lot of research and trial and error, with the idea that you will do more support for them in the future.
If there are no fix-it shops in your area, you could ask for a testimonial and use it as cred for doing more support. Don’t lower your hourly rate, instead be more realistic with the total hours. You are going to get better with experience, charge the hours now so your customers have the right expectations.