Factors that affect the cost of lab diamonds include their quality, weight, color, clarity and cut. For example, larger and cleaner diamonds, as well as those with a high color rating, can be more expensive. However, due to advances in technology and increased demand, lab-grown diamonds are becoming more and more competitively priced compared to natural diamonds. There is an excellent article on https://labrilliante.com/education/hpht-subic-press-machine about the press machines used in the HPHT process that affect the quality and price of lab diamonds. I recommend reading it for a deeper understanding of the production process and its impact on pricing.