You should pay according to the expertise of the tutor, to be the best you should learn from the best if possible.
Learning from someone with experience can provide you with many helpful tips and shortcuts to help you learn quicker.
For a 1-day one-to-one course the tutor will charge their day rate - This is what they earn per day and they will apply this to designing or teaching.
Check out the tutors credentials.
See examples of their work.
Ask how many years of experience they have in the software you need to learn.
Ask if they have any client testimonials you can read.
In particular for 3D printing you should be learning from someone who has experience making the type of product you need to learn to make because additive manufacturing parameters can differ for different products.
It’s not just about designing and printing an item, you will also need to learn how to design it fit for purpose.