Do my customers see the purchase price on their invoice?

No, your customer will only see the price on their invoice that you have entered in the A61partner dashboard for the product in question. The delivery bill contains the products purchased by your customer, as well as a total amount paid by the customer. The total amount is made up of your sales prices.
On the delivery bill you can see the name of your company and, if you want, your personal logo.

In your dashboard you can see which products you have sold. The comparison of purchase price and product price remains exclusively with you.