Another great benefit of lab-created diamonds: you can get them with the impurities you want. Want a red or a blue diamond without the silly price tag? You've got it!
I bought my wife a blue diamond engagement ring in 2010 (blue diamonds have boron in them). The price was pretty good then. I can only imagine that since they've gotten bigger, cheaper, and purer since.
Same process has been done to other gems. I've bought emerald jewelry in the past; all lab-created of course.
For other gem materials, the synthetics are so good and cheap it's embarrassing that expensive jewelry is made from them. You can buy cheap sapphire bar stock[1] or ruby rod[2] on Alibaba. Synthetic emerald gems come in bulk in plastic bags.[3]
Also, just actually checked your links and it's really not what you're describing. Link #1 and #2 are fused silica -- not jewelry gemstone material there. Link #3 isn't even emerald, it's spinel. Synthetic emerald is more expensive.
Yeah, of course, just saying that specific source is obviously bad.
If you're a jeweler you want to get something certified anyway. I don't think a Chinese distributor's claim of AAA-quality emeralds is worth the electrons it took to show it to me.
One thing that's worth keeping in mind is that the usual term for "emerald" in Chinese is 绿宝石, which literally means "green gem". It's understandable that they might be confused about which green gems are actually "emeralds". (That particular ad still doesn't work even if you forgive use of the word emerald, though...)
Your link (3) is deeply troubling. It claims to be "synthetic emerald spinel". Emerald is beryl, not spinel. It claims to have a hardness of 9. That would make it corundum; neither beryl nor spinel is that hard. I'd really rather buy gems from a source that can describe them without contradicting itself in multiple different ways.
You can buy the cut gemstones pretty cheap too. My wife is an artist; she has a massive catalog that contains various created "precious" gemstones for very reasonable prices.
The finished jewelry itself can stand to be more expensive, as creating that piece is an art.
I bought my wife a blue diamond engagement ring in 2010 (blue diamonds have boron in them). The price was pretty good then. I can only imagine that since they've gotten bigger, cheaper, and purer since.
Same process has been done to other gems. I've bought emerald jewelry in the past; all lab-created of course.