I just checked a gold buying site for Warcraft.
The price of 1,000 gold when I quit playing was about $20. It’s now $7.24.
That’s how much the value has depreciated in just 7-8 months.
I don’t play any of these games, but one of the most interesting ones to me (economics-wise) is Second Life, where instead of selling you “Linden dollars” directly they try to match up buy and sell orders, like a real currency exchange.
https://www.xstreetsl.com/modules.php?name=Currency&file=orderlist
I remember reading articles that there were anecdotal reports and official concern that these kind of virtual currencies could be used for money laundering (using fraudulent credit cards, I suppose; the Second Life company tracks your CC info, I think).