Well it looks like high-quality synthetic diamonds are on the way. A recent Wired article discusses two US companies already producing cultured stones. Though both companies plan to sell their stones in the retail jewelry sector; what's really interesting is that both will use the retail sales to fuel research regarding diamond-base semiconductors. That's right in 10 years instead of a silicon-based CPU you may have a diamond-base CPU. UPDATE: Looks like the Japanese got a diamond-based semiconductor to run at 81GHz.
I guess I should be a bit concerned regarding these synthetic stones considering that my family does own a jewelry store and wedding rings are a good % of sales. However, I've never agreed with the whole an engagement ring should cost two-month's salary mantra. And with good reason.