The three-stone engagement ring CAN be more expensive than other engagement ring styles due to the fact that it requires three usually still larger carat weight diamonds (and the larger size means more focus, and more focus usually demands higher attention to diamond quality - which will increase the price). However, this isn't necessarily always the case as three-stone engagement rings can also be made with a variety of diamond shapes, sizes, colorful gemstones, and different precious metals - all of which will ultimately determine the price.

The three-stone engagement ring design allows for a variety of diamond and gemstone shape and size mixing and matching.

1. Round Brilliant: The round brilliant diamond is the most popular diamond shape for engagement rings, including three-stone designs. The round shape is classic, timeless, and offers exceptional sparkle and brilliance.
2. Princess: The princess cut diamond is another popular choice for three-stone engagement rings. The square shape of the princess cut offers a modern and elegant look, with the same sparkle and brilliance as the round brilliant cut.
3. Oval: Oval diamonds have become increasingly popular in recent years, and are a beautiful choice for a three-stone engagement ring. The elongated shape of the oval diamond gives the illusion of a larger diamond, making it a popular choice for those who want a larger look without a larger price tag.
4. Emerald: The emerald cut diamond is a classic and elegant choice for a three-stone engagement ring. The rectangular shape of the emerald cut offers a more understated look, with less sparkle than some other diamond shapes but a beautiful and sophisticated style.
5. Pear: The pear-shaped diamond is another popular choice for a three-stone engagement ring. The teardrop shape of the pear offers a unique and stylish look, with a combination of the sparkle and brilliance of the round brilliant cut and the elongated shape of the oval cut.

Yes, it is possible to mix diamonds and gemstones in a three-stone engagement ring. In fact, many people opt for a combination of diamonds and gemstones to add color and variety to their ring.

Some popular combinations include a center diamond with two gemstones on the sides, or a center gemstone with diamonds on the sides. Popular gemstones for three-stone engagement rings include sapphires, rubies, emeralds, and morganite, among others.

When mixing diamonds and gemstones, it is important to consider the color and clarity of each stone, as well as how they will look together in the ring. A skilled jeweler can help you choose the right combination of stones to create a beautiful and cohesive three-stone engagement ring that fits your preferences and budget.