From pages 404-405 of Milady’s Standard Fundamentals for Estheticians:
There is a difference between high-quality (usually more expensive) and less expensive generic brands. The quality of the products and brushes makes a big difference in how makeup application will go [sic] for you, the artist, or for your client — smoothly or not so smoothly.
Explain to clients why they should buy quality makeup and brushes. Why are they better? Is quality going to make a difference on their skin? Will quality products glide on easier and not tug on the delicate eye tissue? Clients will be more satisfied with products that are easier to work with and will discover that quality is worth the extra money.
From page 437:
Good lighting makes a client look good, and clients who look good are more likely to purchase the products you recommend.
From page 447:
In a [makeup] lesson, clients are shown step by step how to apply makeup. These services are more time-consuming and expensive because you are sharing your knowledge. Lessons are a good opportunity to retail products so clients can reproduce the look you create at home.
Just in case anyone is confused about why we’re all here.