Miley Cyrus attended the world premiere of Avatar: Fire and Ash in Los Angeles with Maxx Morando on Monday night. Her attendance has got everyone talking, but for different reasons. An engagement ring was spotted on Miley's ring finger, and a day later, PEOPLE can confirm that the Flowers singer is engaged.According to an exclusive report from PEOPLE, Miley's engagement ring was designed by Jacquie Aiche. It has been confirmed by Francesca Simons of Francesca Simons Consulting, who is also the designer's representative. The chunky gold ring is a "bespoke" or custom-made piece that was designed specifically for her.Miley Cyrus wore a strapless black Gucci gown to the premiere and kept her accessories to a minimum, so that the engagement ring would shine. The ring is made of a cushion-cut stone, which is embedded in a thick 14-karat gold band.Keep reading to learn more about what experts have to say about Miley Cyrus' engagement ring.Experts estimate the cost of Miley Cyrus' engagement ringMiley Cyrus' chunky gold engagement ring has all eyes on her. Several experts have been trying to guess the approximate price of the 14-karat sparkler. Here are some of the estimates they have made so far.Daniela Tarantino, Blue Nile's VP of merchandising, estimated that the ring could be around $450,000. She explained:"This engagement ring is a chunky gold east-west bezel set ring - a modern and chic trend we are seeing in the bridal industry... We believe the ring is roughly a 4-5 carat modified cushion that costs around $300,000 to $450,000."Another expert who tried to guess the cost of the ring is Reyne Hirsch, Worthy's brand ambassador and former Antiques Roadshow appraiser. They spoke to PEOPLE, saying:"The ring is a stunning with a very modern and minimalist look to it... It's a 4-5 carat, bezel-set, cushion-cut diamond that is set east-to-west. Depending on the color and clarity of the stone, I would suggest a retail value of $150,000-$250,000."The co-founder of Plum Diamonds, Kristy Cullinane, also had a few things to say about Miley Cyrus' ring. She shared:"The diamond appears to be approximately 4 to 5 carats, and the estimated value of the ring would be $200,000+ for a mined diamond or $15,000 for a lab-grown diamond."Miley has been spotted wearing the ring since mid-November this year.Cyrus and Morando seem to be thriving in their relationship, despite the age gap, which was questioned by many initially. A source spoke to PEOPLE last year and shared:"She is very happy with him... Miley has changed a lot in the past couple of years. She seems more calm and harmonious. Everyone loves Maxx. He's a great guy. He's private and doesn't like being in the press. It's been good for her."Miley Cyrus sparked excitement after showing up at the premiere with a clear engagement ring on her finger. PEOPLE later confirmed that she is officially engaged, and experts say her custom gold ring is worth a huge amount. The guesses are between $15,000 to $450,000.Also read: When did Miley Cyrus meet Maxx Morando? Relationship timeline explored as the Flower singer sparks engagement rumors