People do not like to think a lot when they want to buy something. They want to have it easy and enjoy as fast as possible the benefits of what they just bought. Everything that comes between them and the product, any distraction, might end up with frustration and a client that walks away.
So, if you make it easier for your client to buy the extensions they are looking for, reduce the distraction. Here is where bundle deals are coming in. If you do installs and you offering a separate price for the install and for the extensions, your client will start to calculate. She wants to follow the conversation, so she will start to add up every figure you mention. Because beauty and mathematics are dealt by different parts of your brain, the maths are taken care by your brains on the left and the creativity (beauty) by your right side, here it goes wrong. Instead of falling in love with your hair, she will think of buying a calculator and the interest for your products will vanish.
But if you offer a bundle deal for example 14 inch, 16 inch and 18 inch for a fix price or two packs and one closure, the focus stays within the right part of the brains (the right) and the purchase will be made much easier and faster, because no calculations will be done. The same goes if you offer an install and extensions, make it easy and offer one price for the whole treatment, including the hair.
Make the offer attractive and focus on what selling hair is all about, looking and feeling good!