When lab-grown diamonds entered the engagement ring market around 2018-2020, retail prices were 30-50% below natural. The pitch was "same diamond, better price." That part has held up — they are the same physical material.
What didn't hold: the assumption that lab prices would stabilize. Production capacity has roughly tripled every two years. The cost to grow a 1ct stone via Chemical Vapor Deposition (CVD) has dropped from ~$4,000 in 2018 to under $300 in 2026. Retail prices follow production cost on a 12-18 month lag.
A 1ct G/VS2 lab-grown round retailed for ~$2,500 in 2020, ~$1,400 in 2023, and ~$700 in 2026. That's a 70% drop in 6 years.
Resale fell harder. Brilliant Earth and James Allen don't buy back lab-grown except as trade credit toward a new (cheaper) stone. Independent jewelers reject lab outright most of the time — they can't mark it up enough to clear inventory. Pawn shops take it at 5-10% of retail. Private resale (IDoNowIDont, WP Diamonds, Worthy) yields 15-25% of original retail when it sells, which is rarely.
If you bought a lab diamond in 2021 for $2,200 expecting some residual value: realistic 2026 resale is $200-450. The actual stone is unchanged — same brilliance, same clarity. The market for it just kept getting cheaper.
This is not a reason to avoid lab-grown if you're buying for sentiment and don't plan to sell. It IS a reason not to think of lab-grown as an investment or even as a holds-its-value purchase. For that, only natural-diamond engagement rings (or no diamond at all) work.