Just saying, for anyone dropping in: The diamond education and vending site of Pricescope.com is a great resource. Once you join and log in, there's a "Preloved PS Jewels" section (you can only get to when logged in) where members advertise jewelry they are selling privately. LoupeTroop.com and DiamondBistro.com are sites where Pricescope and other people advertise diamonds and jewelry for sale. LoveAffairDiamonds.com has vintage, antique, secondhand, and consignment rings and diamonds. JewelsByGrace.com is another. Both of those are Pricescope members who have been in the business for years.
A well-cut CZ seems very hard to find nowadays. Those cut my "Interlap" and sold by Wink Jones at a site that was called FreeCZ.com were some of the very best. But that quality of CZ is not readily available nowadays.
What has replaced CZ is varieties of Moissanite, or silicon carbide. The new Amora Gems, and some competitors sold by Joseph Schubach Jewelers look awesome and very diamond-like, without the performance drop-off CZs had when dirty. Dirty moissanite still performs. Betterthandiamond.com for Amora Gems, and you can find them other places, too. Moissanite now comes in numerous makes like hearts & arrows round, Old European Cut, asscher, princess, oval, marquise. And the colors range from D/E colorless down into the more typical J/K warm tones into some more brownish or grayish colors. There are copies of Good Old Gold's "August Vintage" OEC round diamonds, in Amora. Over at TheFacetLounge is where I saw the elongated antique cushion cut stones that Joseph Schubach is offering.
There are not only alternatives to diamond, there are more ways than one to get a ring that makes one happy. I'm one of those over-50 women with a gorgeous big rock on my hand. But dangit, people, no man gifted it to me. I got on Pricescope a long time ago, learned all I could about diamonds and what I like in a diamond. They I (gasp!) BOUGHT IT MYSELF, FOR ME! To this day, I still get called selfish and shallow. Well, we don't really see many MEN depriving themselves of "toys" or luxury goods that they can afford, now do I?? ( hahahahahaha! I'm single and childfree. I don't need anyone's permission.) The prices of diamonds go up and down, but mostly up over time. Quality holds its value. Average and below-average do not. Cut is king. Demand for diamonds in the USA may be flat or decreasing, but there is all of China and other parts of the world where diamonds are just taking off. Prices are all supply and demand, and boom/bust. There have been times where Pricescope people sold a high-end diamond for more than they paid. Online vendors work on much smaller margins, said to be more like 15%-20% and not the 100% or more that were common when brick and mortar jewelers ruled. Two diamond vendors that have found some very nice diamonds for people on a budget are I.D. Jewelry and B2CJewels. Both are Pricescope vendors. James Allen is also good, but what you have to know about their site is that many diamonds on it are "virtual stones" still held by cutters, and those could have been already sold but are still showing up on online databases such as James Allen uses.